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VulnerabilityPublished Updated

CVE-2026-88359: libfyaml · Unthrottled Resource Allocation

Affects libfyamlSource CVE Database V5

0

Not known to be exploited · CVSS 6.5 Medium : upgrade to 0.9.6 when convenient.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.9.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: 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 26 Oct 2026.

What to do

Upgrade pantoniou/libfyaml to 0.9.6.

Affected software

ProductAffectedFixed in
GitHubpantoniou/libfyamlpkg:github/pantoniou/libfyamlOther threatsAffected
  • <0.9.6
Fixed in
  • 0.9.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid processing untrusted YAML documents containing very large literal or folded block scalars to mitigate risk.

Description

libfyaml version 0.9.6 and earlier contain a stack exhaustion vulnerability in the function fy_atom_iter_format(). This occurs when processing specially crafted YAML documents with very large literal or folded block scalars, causing repeated allocation of stack memory inside a loop. The cumulative stack growth can exceed the process stack limit, leading to a segmentation fault (SIGSEGV) and denial of service.

References

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