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.
Analysis and contextual insights are available on OpenCVE Cloud.
Vendor Workaround
Split any untrusted comment string on line breaks and pass the resulting list as the comment element of the {comment, data} tuple. Ymlr prefixes every list element with its own # marker, so no line can leave the comment context. Alternatively, reject comment strings that contain carriage return or line feed characters, or keep untrusted text out of comments entirely and place it in the encoded data instead, where the encoder quotes it.
Tracking
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Fri, 31 Jul 2026 15:30:00 +0000
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ssvc
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Fri, 31 Jul 2026 14:00:00 +0000
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| 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. | |
| Title | YAML injection via unescaped newlines in ymlr document comments | |
| First Time appeared |
Ufirstgroup
Ufirstgroup ymlr |
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| Weaknesses | CWE-93 | |
| CPEs | cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Ufirstgroup
Ufirstgroup ymlr |
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| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-07-31T14:28:44.562Z
Reserved: 2026-07-22T13:58:26.233Z
Link: CVE-2026-65636
Updated: 2026-07-31T14:28:39.454Z
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