CVE-2026-65636
YAML injection via unescaped newlines in ymlr document comments
Description
Improper Neutralization of CRLF Sequences vulnerability in ufirstgroup ymlr (Elixir.Ymlr module) allows attackers to inject arbitrary content into generated YAML documents through document comments. Ymlr.document!/2 interpolates each caller-supplied comment string into the output behind a single # prefix without validating it or escaping line breaks. Because a YAML comment is terminated by a line break, the first carriage return or line feed in the comment string ends the comment context and everything after it is emitted at column 0 of the document body. An attacker who controls text that the host application passes as a comment can forge top-level mapping keys, override values the application itself set, and emit --- or ... markers that split the output into additional documents. Downstream consumers of the generated YAML, such as configuration loaders, deployment manifests, CI pipelines and data importers, parse the injected content as legitimate data. The same clause backs Ymlr.document/2, Ymlr.documents!/2 and Ymlr.documents/2, so every document encoding entry point is affected. This vulnerability is associated with program files lib/ymlr.ex and program routines 'Elixir.Ymlr':document!/2, 'Elixir.Ymlr':documents!/2. This issue affects ymlr from 0.0.1 before 5.1.6.
INFO
Published Date :
July 31, 2026, 2:16 p.m.
Last Modified :
July 31, 2026, 3:18 p.m.
Remotely Exploit :
No
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Affected Products
The following products are affected by CVE-2026-65636
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | LOW | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | LOW | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update the ymlr dependency to version 5.1.6 or later.
- Validate and sanitize all comment strings before passing them to Ymlr.
- Review downstream YAML consumers for security implications.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-65636.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-65636 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-65636
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-65636 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-65636 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 31, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-65636', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-31T14:28:31.525792Z'} -
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Jul. 31, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/ufirstgroup/ymlr', 'vendor': 'ufirstgroup', 'modules': ['Elixir.Ymlr'], 'product': 'ymlr', 'versions': [{'status': 'affected', 'version': '0.0.1', 'lessThan': '5.1.6', 'versionType': 'semver'}], 'packageURL': 'pkg:hex/ymlr', 'packageName': 'ymlr', 'programFiles': ['lib/ymlr.ex'], 'collectionURL': 'https://repo.hex.pm', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Ymlr':document!/2"}, {'name': "'Elixir.Ymlr':documents!/2"}]}, {'cpes': ['cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/ufirstgroup/ymlr', 'vendor': 'ufirstgroup', 'modules': ['Elixir.Ymlr'], 'product': 'ymlr', 'versions': [{'status': 'affected', 'version': '0c11a86de83825e91c27cecaccb03f36416d8fe0', 'lessThan': '42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc', 'versionType': 'git'}], 'packageURL': 'pkg:github/ufirstgroup/ymlr', 'packageName': 'ufirstgroup/ymlr', 'programFiles': ['lib/ymlr.ex'], 'collectionURL': 'https://github.com', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.Ymlr':document!/2"}, {'name': "'Elixir.Ymlr':documents!/2"}]}] Added Description Improper Neutralization of CRLF Sequences vulnerability in ufirstgroup ymlr (Elixir.Ymlr module) allows attackers to inject arbitrary content into generated YAML documents through document comments. Ymlr.document!/2 interpolates each caller-supplied comment string into the output behind a single # prefix without validating it or escaping line breaks. Because a YAML comment is terminated by a line break, the first carriage return or line feed in the comment string ends the comment context and everything after it is emitted at column 0 of the document body. An attacker who controls text that the host application passes as a comment can forge top-level mapping keys, override values the application itself set, and emit --- or ... markers that split the output into additional documents. Downstream consumers of the generated YAML, such as configuration loaders, deployment manifests, CI pipelines and data importers, parse the injected content as legitimate data. The same clause backs Ymlr.document/2, Ymlr.documents!/2 and Ymlr.documents/2, so every document encoding entry point is affected. This vulnerability is associated with program files lib/ymlr.ex and program routines 'Elixir.Ymlr':document!/2, 'Elixir.Ymlr':documents!/2. This issue affects ymlr from 0.0.1 before 5.1.6. Added CVSS V4.0 AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-93 Added Reference https://cna.erlef.org/cves/CVE-2026-65636.html Added Reference https://github.com/ufirstgroup/ymlr/commit/42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc Added Reference https://github.com/ufirstgroup/ymlr/commit/7e53061fb2809b787fba0373c46b78e253c83adc Added Reference https://github.com/ufirstgroup/ymlr/security/advisories/GHSA-p8qx-7cp9-v6c9 Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-65636