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VulnerabilityPublished Updated

CVE-2026-4177: TODDR YAML::Syck · Heap-based Buffer Overflow

Affects TODDR YAML::SyckSource CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.

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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 16 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
TODDRYAML::SyckAffected
  • <=1.36
Fixed in–
GitHubYAML-Syckpkg:github/YAML-SyckOther threatsAffected
  • <=1.36
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

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