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CVE-2026-65636· NVD / CVE Program· CNA EEF

YAML injection via unescaped newlines in ymlr document comments

Noroxi assessment

Priority: Monitor (action score 8/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Someone with local access to the system can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: ufirstgroup ymlr 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc, 5.1.6.

Low priority for now. Upgrade to ufirstgroup ymlr 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dc, 5.1.6 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

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.

LowCVSS 2.1 · v4.0—No exploit Fix available
Published
Jul 31, 2026
Updated
Aug 4, 2026
EPSS
0.2% · 9th percentile

Report tools

JSON

Action score

8

Monitor

Low priority for now.

CVSS
8 / 40 · 2.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
2.1
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • ufirstgroup ymlr

    • 0.0.1 and later · before 5.1.6affected · semver
    • 0c11a86de83825e91c27cecaccb03f36416d8fe0 and later · before 42a0bf8b2af44b0e7c42d0b7044c8588ca5866dcaffected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Hexymlrfrom 0.0.1 · before 5.1.65.1.6

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
ufirstgroup ymlr42a0bf8b2af44b0e7c42d0b7044c8588ca5866dcVendor (CNA)
ufirstgroup ymlr5.1.6Vendor (CNA)
Hex:ymlr5.1.6Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records