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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.45%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- EPSS
- 0.45% probability · 39th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-122, CWE-120
- Affected
- toddr/yaml\
- Source
- 9b29abf9-4ab0-4765-b253-1875cd9b441e
EPSS 0.4% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patchPatch
- https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21Release Notes
- http://www.openwall.com/lists/oss-security/2026/03/16/6Mailing List, Third Party Advisory
- 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.