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Review reviewCritical

CVE-2026-4177

TODDR YAML::Syck, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8

YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter. The heap overflow occurs when class names exceed the initial 512-byte allocation. The base64 decoder could read past the buffer end on trailing newlines. strtok mutated n->type_id in place, corrupting shared node data. A memory leak occurred in syck_hdlr_add_anchor when a node already had an anchor. The incoming anchor string 'a' was leaked on early return.

CVSS
9.1
EPSS
0.43%
35.3% percentile
CISA KEV
Not listed
Published
2026.03.17
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.43%
Technical severityCVSS 9.1

Vulnerability overview

YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter. The heap overflow occurs when class names exceed the initial 512-byte allocation. The base64 decoder could read past the buffer end on trailing newlines. strtok mutated n->type_id in place, corrupting shared node data. A memory leak occurred in syck_hdlr_add_anchor when a node already had an anchor. The incoming anchor string 'a' was leaked on early return.

Affected product and versions

Product
TODDR YAML::Syck, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8
Affected versions
<= 1.36, < 1.37
Fixed versions
1.37

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that TODDR YAML::Syck, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CWE
CWE-120, CWE-122
CVE-2026-4177 — TODDR YAML::Syck, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8 | SECUFOCUS NOW