YAML injection via unescaped comment newlines
Published Jul 31, 2026 · Updated Jul 31, 2026
YAML injection in UFirst Group ymlr 0.0.1 through 5.1.5 allows attackers to alter generated documents through untrusted comments. The document!/2 comment clause prefixes each caller-supplied string only once, so an embedded carriage return or line feed ends the comment and emits the remainder as YAML at column zero. Exploitation requires a host application to place attacker-controlled text in a document comment; downstream parsers then accept forged keys or extra documents as legitimate data.
Summary
What happened
YAML injection in UFirst Group ymlr 0.0.1 through 5.1.5 allows attackers to alter generated documents through untrusted comments. The document!/2 comment clause prefixes each caller-supplied string only once, so an embedded carriage return or line feed ends the comment and emits the remainder as YAML at column zero. Exploitation requires a host application to place attacker-controlled text in a document comment; downstream parsers then accept forged keys or extra documents as legitimate data.
The record
- CVE
- CVE-2026-65636
- Published
- Jul 31, 2026
- Updated
- Jul 31, 2026
- Vendor
- UFirst Group
- Product
- ymlr
- Classifications
- CWE-93, CAPEC-15, T1565.001
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 31, 2026CVE publishedPublication date reported by the CVE source.
- Jul 31, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.0.1 <5.1.6
- Affected versionversion=0c11a86de83825e91c27cecaccb03f36416d8fe0 <42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-p8qx-7cp9-v6c9 proof-of-concept scriptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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