FKIE_CVE-2026-65636
Vulnerability from fkie_nvd - Published: 2026-07-31 14:16 - Updated: 2026-08-04 14:52
Severity
Summary
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
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"Elixir.Ymlr"
],
"packageName": "ymlr",
"packageURL": "pkg:hex/ymlr",
"product": "ymlr",
"programFiles": [
"lib/ymlr.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Ymlr\u0027:document!/2"
},
{
"name": "\u0027Elixir.Ymlr\u0027:documents!/2"
}
],
"repo": "https://github.com/ufirstgroup/ymlr",
"vendor": "ufirstgroup",
"versions": [
{
"lessThan": "5.1.6",
"status": "affected",
"version": "0.0.1",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:ufirstgroup:ymlr:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"Elixir.Ymlr"
],
"packageName": "ufirstgroup/ymlr",
"packageURL": "pkg:github/ufirstgroup/ymlr",
"product": "ymlr",
"programFiles": [
"lib/ymlr.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Ymlr\u0027:document!/2"
},
{
"name": "\u0027Elixir.Ymlr\u0027:documents!/2"
}
],
"repo": "https://github.com/ufirstgroup/ymlr",
"vendor": "ufirstgroup",
"versions": [
{
"lessThan": "42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc",
"status": "affected",
"version": "0c11a86de83825e91c27cecaccb03f36416d8fe0",
"versionType": "git"
}
]
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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.\n\nAn 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.\n\nThis vulnerability is associated with program files lib/ymlr.ex and program routines \u0027Elixir.Ymlr\u0027:document!/2, \u0027Elixir.Ymlr\u0027:documents!/2.\n\nThis issue affects ymlr from 0.0.1 before 5.1.6."
}
],
"id": "CVE-2026-65636",
"lastModified": "2026-08-04T14:52:54.493",
"metrics": {
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 2.1,
"baseSeverity": "LOW",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "LOW",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "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/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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-65636",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-31T14:28:31.525792Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-31T14:16:51.240",
"references": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://cna.erlef.org/cves/CVE-2026-65636.html"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/ufirstgroup/ymlr/commit/42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/ufirstgroup/ymlr/commit/7e53061fb2809b787fba0373c46b78e253c83adc"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/ufirstgroup/ymlr/security/advisories/GHSA-p8qx-7cp9-v6c9"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-65636"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-93"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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