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A File Format to Aid in Security Vulnerability Disclosure
contact@edoverflow.com
Nightwatch Cybersecurity
yakov+ietf@nightwatchcybersecurity.com
When security vulnerabilities are discovered by
researchers, proper reporting channels are often lacking. As a result,
vulnerabilities may be left unreported. This document defines a machine-parsable format
("security.txt") to help organizations describe their vulnerability disclosure practices
to make it easier for researchers to report vulnerabilities.
Introduction
Motivation, Prior Work, and Scope
Many security researchers encounter situations where they are unable
to report security vulnerabilities to organizations because there are
no reporting channels to contact the owner of a particular
resource, and no information is available about the vulnerability disclosure practices
of such owner.
As per
There are also contact conventions prescribed for Internet Service Providers (ISPs)
in
In this document, we define a richer, machine-parsable, and more extensible way
for organizations to communicate information about their security disclosure
practices and ways to contact them. Other details of vulnerability disclosure
are outside the scope of this document. Readers are encouraged to consult other
documents such as
As per
The "security.txt" file is intended to be complementary and not a substitute
or replacement for other public resources maintained by organizations regarding
their security disclosure practices.
Terminology
The key words "MUST ", "MUST NOT ", "REQUIRED ", "SHALL ", "SHALL NOT ",
"SHOULD ", "SHOULD NOT ", "RECOMMENDED ", "NOT RECOMMENDED ", "MAY ", and
"OPTIONAL " in this document are to be interpreted as described in
BCP 14
The term "researcher" corresponds
to the terms "finder" and "reporter" in
The term "implementors" includes all parties involved in
the vulnerability disclosure process.
The Specification
This document defines a text file to be placed in a known location
that provides information about vulnerability disclosure practices of a particular organization.
The format of this file is machine parsable and MUST follow the ABNF grammar defined in
By convention, the file is named "security.txt". The location and scope are described
in
This text file contains multiple fields with different values. A field contains a "name", which is the first part of a field all the way up
to the colon (for example: "Contact:") and follows the syntax defined for "field-name" in MAY also contain blank lines.
A field MUST always consist of a name and a value
(for example: "Contact: mailto:security@example.com"). A "security.txt" file
can have an unlimited number of fields. Each field MUST appear on
its own line. Unless otherwise specified by the field definition,
multiple values MUST NOT be chained together for a single field.
Unless otherwise indicated in a definition of a particular field, a field MAY appear
multiple times.
Implementors should be aware that some of the fields may
contain URIs using percent-encoding (as per
Comments
Any line beginning with the "#" (%x23) symbol MUST be interpreted as a comment. The content of the comment may contain any ASCII or Unicode characters in the
%x21-7E and %x80-FFFFF ranges plus the tab (%x09) and space (%x20) characters.
Example:
Line Separator
Every line MUST end with either a carriage return and line feed
characters (CRLF / %x0D %x0A) or just a line feed character (LF / %x0A).
Digital Signature
It is RECOMMENDED that a "security.txt" file be digitally signed
using an OpenPGP cleartext signature as described in RECOMMENDED that organizations use the "Canonical" field (as per
When it comes to verifying the key used to generate the signature, it is always
the security researcher's responsibility to make sure the key being
used is indeed one they trust.
Extensibility
Like many other formats and protocols, this format may need to be changed
over time to fit the ever-changing landscape of the Internet. Therefore,
extensibility is provided via an IANA registry for fields as defined
in MUST be
considered optional. To encourage extensibility and interoperability,
researchers MUST ignore any fields they do not explicitly support.
In general, implementors should "be conservative in what you do,
be liberal in what you accept from others" (as per
Field Definitions
Unless otherwise stated, all fields MUST be considered optional.
Acknowledgments
The "Acknowledgments" field indicates a link to a page where security
researchers are recognized for their reports. The page being referenced
should list security researchers that reported security vulnerabilities
and collaborated to remediate them. Organizations should be careful
to limit the vulnerability information being published in order
to prevent future attacks.
If this field indicates a web URI, then it MUST begin with "https://"
(as per
Example:
Example security acknowledgments page:
Canonical
The "Canonical" field indicates the canonical URIs where the "security.txt" file is located,
which is usually something like "https://example.com/.well-known/security.txt".
If this field indicates a web URI, then it MUST begin with "https://"
(as per
While this field indicates that a "security.txt" retrieved from a given URI
is intended to apply to that URI, it MUST NOT be interpreted to apply to
all canonical URIs listed within the file. Researchers SHOULD use an additional
trust mechanism such as a digital signature (as per
If this field appears within a "security.txt" file and the URI used to
retrieve that file is not listed within any canonical fields,
then the contents of the file SHOULD NOT be trusted.
Contact
The "Contact" field indicates a method that researchers
should use for reporting security
vulnerabilities such as an email address, a phone number, and/or a
web page with contact information. This field MUST
always be present in a "security.txt" file. If this field indicates a web URI,
then it MUST begin with "https://" (as per
The value MUST follow the URI syntax described in RECOMMENDED that encryption be used (as per
These SHOULD be listed in order of preference, with the first occurrence being the preferred
method of contact, the second occurrence being the second most preferred method of contact, etc. In the example below, the first email address
("security@example.com") is the preferred method of contact.
Encryption
The "Encryption" field indicates an encryption key that
security researchers should use for encrypted communication. Keys MUST NOT
appear in this field. Instead, the value of this field
MUST be a URI pointing to a location where the key can be retrieved.
If this field indicates a web URI, then it MUST begin with "https://"
(as per
When it comes to verifying the authenticity of the key, it is always the security
researcher's responsibility to make sure the key being specified is indeed one
they trust. Researchers must not assume that this key is
used to generate the digital signature referenced in
Example of an OpenPGP key available from a web server:
Example of an OpenPGP key available from an OPENPGPKEY DNS record:
Example of an OpenPGP key being referenced by its fingerprint:
Expires
The "Expires" field indicates the date and time after which the data contained in the "security.txt"
file is considered stale and should not be used (as per RECOMMENDED that the value
of this field be less than a year into the future to avoid staleness.
This field MUST always be present and MUST NOT appear more than once.
Hiring
The "Hiring" field is used for linking to the vendor's security-related job positions.
If this field indicates a web URI, then it MUST begin with "https://"
(as per
Policy
The "Policy" field indicates a link to where the vulnerability disclosure policy is located.
This can help security researchers understand
the organization's vulnerability reporting practices.
If this field indicates a web URI, then it MUST begin with "https://"
(as per
Example:
Preferred-Languages
The "Preferred-Languages" field can be used to indicate a set of natural languages that
are preferred when submitting security reports. This set MAY list multiple
values, separated by commas. If this field is included, then at least
one value MUST be listed. The values within this set are language tags
(as defined in
The order in which they appear is not an indication of priority;
the listed languages are intended to have equal priority.
This field MUST NOT appear more than once.
Example (English, Spanish and French):
Example of an Unsigned "security.txt" File
Example of a Signed "security.txt" File
Location of the security.txt File
For web-based services, organizations MUST place the "security.txt" file under the "/.well-known/" path, e.g., https://example.com/.well-known/security.txt
as per MUST be used.
The file MUST be accessed via HTTP 1.0 or a higher version,
and the file access MUST use the "https" scheme (as per MUST have a Content-Type of "text/plain"
with the default charset parameter set to "utf-8" (as per
Retrieval of "security.txt" files and resources indicated within such files may result in a redirect (as per
Scope of the File
A "security.txt" file MUST only apply to the domain
or IP address in the URI used to retrieve it, not to any of its subdomains or parent domains.
A "security.txt" file MAY also apply to products and services provided by the organization publishing the file.
As per
Organizations SHOULD use the policy directive (as per
Some examples appear below:
File Format Description and ABNF Grammar
The file format of the "security.txt" file MUST be plain text (MIME type "text/plain") as defined
in MUST be encoded using UTF-8
The format of this file MUST follow the ABNF definition below (which incorporates the core ABNF rules from
lang-tag = < Language-Tag from Section 2.1 of [RFC5646] >
lang-values = lang-tag *(*WSP "," *WSP lang-tag)
uri = < URI as per Section 3 of [RFC3986] >
ext-field = field-name fs SP unstructured
field-name = < imported from Section 3.6.8 of [RFC5322] >
unstructured = < imported from Section 3.2.5 of [RFC5322] >
token = < imported from Section 5.1 of [RFC2045] >
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
BIT = "0" / "1"
CHAR = %x01-7F
; any 7-bit US-ASCII character,
; excluding NUL
CR = %x0D
; carriage return
CRLF = CR LF
; Internet standard newline
CTL = %x00-1F / %x7F
; controls
DIGIT = %x30-39
; 0-9
DQUOTE = %x22
; " (Double Quote)
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
HTAB = %x09
; horizontal tab
LF = %x0A
; linefeed
LWSP = *(WSP / CRLF WSP)
; Use of this linear-white-space rule
; permits lines containing only white
; space that are no longer legal in
; mail headers and have caused
; interoperability problems in other
; contexts.
; Do not use when defining mail
; headers and use with caution in
; other contexts.
OCTET = %x00-FF
; 8 bits of data
SP = %x20
VCHAR = %x21-7E
; visible (printing) characters
WSP = SP / HTAB
; white space
]]>
"ext-field" refers to extension fields, which are discussed in
Security Considerations
Because of the use of URIs and well-known resources, security considerations of
Compromised Files and Incident Response
An attacker that has compromised a website is able to compromise
the "security.txt" file as well or set up a redirect to their own site.
This can result in security reports not being received by the organization
or being sent to the attacker.
To protect against this, organizations should use the "Canonical" field to indicate the locations
of the file (as per
Security researchers should validate the "security.txt" file, including verifying
the digital signature and checking any available historical records before using the information
contained in the file. If the "security.txt" file looks suspicious or compromised,
it should not be used.
While it is not recommended, implementors may choose to use the information published
within a "security.txt" file for an incident response. In such cases, extreme caution
should be taken before trusting such information, since
it may have been compromised by an attacker. Researchers should use additional methods
to verify such data including out-of-band verification of the Pretty Good Privacy (PGP) signature, DNSSEC-based approaches, etc.
Redirects
When retrieving the file and any resources referenced in the file, researchers should record
any redirects since they can lead to a different domain or IP address controlled by an attacker. Further
inspection of such redirects is recommended before using the information contained within the file.
Incorrect or Stale Information
If information and resources referenced in a "security.txt" file are incorrect
or not kept up to date, this can result in security reports not being received
by the organization or sent to incorrect contacts, thus exposing possible
security issues to third parties. Not having a "security.txt" file may be preferable
to having stale information in this file. Organizations must use
the "Expires" field (see
Organizations should ensure that information in this file and any referenced
resources such as web pages, email addresses, and telephone numbers
are kept current, are accessible, are controlled by the organization,
and are kept secure.
Intentionally Malformed Files, Resources, and Reports
It is possible for compromised or malicious sites to create files that are extraordinarily
large or otherwise malformed in an attempt to discover or exploit weaknesses
in the parsing code.
Researchers should make sure that any such code
is robust against large or malformed files and fields, and they may choose to have the code not parse files larger than 32 KBs, those with fields longer than 2,048 characters, or those containing more than 1,000 lines. The ABNF grammar (as defined in
The same concerns apply to any other resources referenced within "security.txt"
files, as well as any security reports received as a result of publishing
this file. Such resources and reports may be hostile, malformed, or malicious.
No Implied Permission for Testing
The presence of a "security.txt" file might be interpreted by researchers
as providing permission to do security testing against the domain or IP address
where it is published or against products and services provided by the organization publishing
the file.
This might result in increased testing against an organization by researchers. On the other hand, a decision not
to publish a "security.txt" file might be interpreted by the
organization operating that website to be a way to signal to researchers
that permission to test that particular site or project is denied. This might result in pushback against
researchers reporting security issues to that organization.
Therefore, researchers shouldn't assume that the presence or absence of
a "security.txt" file grants or denies permission for security testing.
Any such permission may be indicated in the company's vulnerability disclosure policy
(as per
Multi-User Environments
In multi-user / multi-tenant environments, it may be possible for a user to take
over the location of the "security.txt" file. Organizations should reserve
the "security.txt" namespace at the root to ensure no third party can create a page with
the "security.txt" AND "/.well-known/security.txt" names.
Protecting Data in Transit
To protect a "security.txt" file from being tampered with in transit, implementors MUST use
HTTPS (as per
The certificate may also be checked for revocation via the Online Certificate Status
Protocol (OCSP)
In cases where the "security.txt" file cannot be served via HTTPS (such as localhost) or is
being served with an invalid certificate, additional human validation is recommended since
the contents may have been modified while in transit.
As an additional layer of protection, it is also recommended that
organizations digitally sign their "security.txt" file with OpenPGP (as per
However, the determination of validity of such keys is out of scope
for this specification. Security researchers need to establish other secure means to
verify them.
Spam and Spurious Reports
Similar to concerns in
Organizations need to weigh the advantages of publishing this file versus
the possible disadvantages and increased resources required to analyze
security reports.
Security researchers should review all information within the "security.txt"
file before submitting reports in an automated fashion or reports resulting from automated scans.
IANA Considerations
Implementors should be aware that any resources referenced within
a "security.txt" file MUST NOT point to the Well-Known URIs namespace unless
they are registered with IANA (as per
Well-Known URIs Registry
IANA has updated the "Well-Known URIs" registry with the following additional
values (using the template from
Registry for security.txt Fields
IANA has created the "security.txt Fields" registry in
accordance with
New registrations or updates MUST be published in accordance with the
"Expert Review" guidelines as described in Sections
Designated experts should determine whether a proposed registration or update
provides value to organizations and researchers using this format and makes sense in the context of industry-accepted vulnerability disclosure processes
such as
New registrations and updates MUST contain the following information:
Existing registrations may be marked historic or deprecated, as appropriate, by a future update to this document.
The initial registry contains these values:
References
Normative References
Informative References
Date and time - Representations for information interchange - Part 1: Basic rules
ISO
Date and time - Representations for information interchange - Part 2: Extensions
ISO
Information technology - Security techniques - Vulnerability disclosure
ISO
The CERT Guide to Coordinated Vulnerability Disclosure
Software Engineering Institute
Carnegie Mellon University, CMU/SEI-2017-SR-022
Acknowledgments
The authors would like to acknowledge the help provided during the
development of this document by
The authors would also like to acknowledge the feedback provided by multiple members of the IETF's
LAST CALL, SAAG, and SECDISPATCH lists.
- Matching is performed only against the DNS-ID identifiers.
- DNS domain names in server certificates
MAY contain the wildcard character '*' as the complete leftmost label within the identifier.
- URI suffix:
- security.txt
- Change controller:
- IETF
- Specification document(s):
- RFC 9116
- Status:
- permanent
- Name of the field being registered or updated
- Short description of the field
- Whether the field can appear more than once
-
New or updated status, which MUST be one of the following:- current:
- The field is in current use.
- deprecated:
- The field has been in use, but new usage is discouraged.
- historic:
- The field is no longer in current use.
- Change controller
- The document in which the specification of the field is published (if available)
- Field Name:
- Acknowledgments
- Description:
- link to page where security researchers are recognized
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Canonical
- Description:
- canonical URI for this file
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Contact
- Description:
- contact information to use for reporting vulnerabilities
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Expires
- Description:
- date and time after which this file is considered stale
- Multiple Appearances:
- no
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Encryption
- Description:
- link to a key to be used for encrypted communication
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Hiring
- Description:
- link to the vendor's security-related job positions
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Policy
- Description:
- link to security policy page
- Multiple Appearances:
- yes
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116
- Field Name:
- Preferred-Languages
- Description:
- list of preferred languages for security reports
- Multiple Appearances:
- no
- Status:
- current
- Change controller:
- IETF
- Reference:
- RFC 9116