CVE-2026-4177YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter
- 9.1CriticalCVSS base score
- 0.48%Exploitation in 30 daysEPSS · top 58% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By CPANSec
- 2 days later
· 2 days later
Published
- 4 months later
· 4 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Critical9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H |
| redhat-SADPADP (enrichment) | 3.1 | High7.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L |
| NVDNVD · Modified | 3.1 | Critical9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.48% · top 58% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.1.
Affected products
- affected ≤ 1.36
What to do
Solution: Upgrade to version 1.37 or higher.
References
References8
- https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch (opens in a new tab)patch
- https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21 (opens in a new tab)release-notes
- http://www.openwall.com/lists/oss-security/2026/03/16/6 (opens in a new tab)
- https://access.redhat.com/security/cve/CVE-2026-4177 (opens in a new tab)vdb-entryx_refsource_REDHAT
- RHBZ#2448277 (opens in a new tab)issue-trackingx_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4177.json (opens in a new tab)x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:8311 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:6470 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-12523 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-4177)Record last updated .