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VulnerabilityPublished

CVE-2026-65636: ufirstgroup ymlr · CRLF Injection

Affects ufirstgroup ymlrSource CVE Database V5

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Not known to be exploited · CVSS 2.1 Low : upgrade to 5.1.6 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 4.0 base score
2.1Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 5.1.6, 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 31 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade ymlr to 5.1.6; ymlr to 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc.

Affected software

ProductAffectedFixed in
ufirstgroupymlrAffected
  • >=0.0.1 <5.1.6
Fixed in
  • 5.1.6
ufirstgroupymlrAffected
  • ≥ 0c11a86de83825e91c27cecaccb03f36416d8fe0, < 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc
Fixed in
  • 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc
Hexymlrpkg:hex/ymlrOther threatsAffected
  • >=0.0.1 <5.1.6
Fixed in
  • 5.1.6

CPE configurations (1)

  • cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid passing untrusted or attacker-controlled strings as comments to the ymlr document generation functions. Validate or sanitize comment inputs to remove CRLF characters or other control characters that could terminate comments prematurely.

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.

References

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