CVE-2026-88359: libfyaml · Unthrottled Resource Allocation
Affects libfyamlSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 24 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 2026.
What to do
Upgrade pantoniou/libfyaml to 0.9.6.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
GitHubpantoniou/libfyamlpkg:github/pantoniou/libfyamlOther 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
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.