CVE-2026-4177: TODDR YAML::Syck · Heap-based Buffer Overflow
Affects TODDR YAML::SyckSource CVE Database V5
Not known to be exploited · CVSS 9.1 Critical.
Data as of 30 Oct 2026, 11:52 UTC
Contested
Critical score, yet low EPSS after six months- EPSS
- 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| TODDRYAML::Syck | Affected
| Fixed in– |
GitHubYAML-Syckpkg:github/YAML-SyckOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Red Hat has released security updates addressing CVE-2026-4177 in perl-YAML-Syck packages for Red Hat Enterprise Linux 7 Extended Lifecycle Support. Users should apply these official patches promptly to remediate the vulnerabilities. Refer to Red Hat advisories RHSA-2026:8311 and RHSA-2026:6470 for update instructions. Patch status is confirmed with official fixes available. No additional mitigations are indicated beyond applying the vendor-provided updates.
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.
References
- github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch (opens in a new tab)
- metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes (opens in a new tab)
- openwall.com/lists/oss-security/2026/03/16/6 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-4177 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2448277 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4177.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:8311 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:6470 (opens in a new tab)