CVE-2026-65636: YAML injection via unescaped newlines in ymlr document comments

Official 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.

Vendor	Product	Versions
ufirstgroup	ymlr	0.0.1 – before 5.1.6
ufirstgroup	ymlr	0c11a86de83825e91c27cecaccb03f36416d8fe0 – before 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc

Vendor

Product

Versions

0.0.1 – before 5.1.6

0c11a86de83825e91c27cecaccb03f36416d8fe0 – before 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc

CVE-2026-65636YAML injection via unescaped newlines in ymlr document comments

In plain English

Official description

Affected products (as reported)

References