What’s Vulnerable › Vulnerabilities

CVE-2026-4177: YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-16 · updated 2026-07-15
• Weakness: CWE-122

Description

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 products

• TODDR Yaml::Syck: before 1.37 — fixed in 1.37

How to fix

Upgrade to a fixed version: TODDR Yaml::Syck 1.37. Check the vendor advisory for mitigations.

References

• https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch
• https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21
• http://www.openwall.com/lists/oss-security/2026/03/16/6
• https://access.redhat.com/errata/RHSA-2026:6470
• https://access.redhat.com/errata/RHSA-2026:8311
• https://access.redhat.com/security/cve/CVE-2026-4177
• https://bugzilla.redhat.com/show_bug.cgi?id=2448277
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4177.json

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