CVE-2026-88359

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-09-24. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 3 sources updated this weekElevated
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.5Exploit: Elevated riskExposed services: Not assessed

An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.

libfyaml 0.9.6 contains a stack exhaustion vulnerability in fy_atom_iter_format(). When processing a specially crafted YAML document containing a very large literal or folded block scalar, the function repeatedly grows an internal buffer using alloca() inside a loop. The allocated stack memory is not released until the function returns, causing cumulative stack growth that can exceed the process stack limit and result in SIGSEGV and denial of service.

CVSS v3
6.5
EG Score
6.5MEDIUMhigh confidence
EG Risk
45
EG Risk 45/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.
EPSS PROB
0.2%
EPSS %ILE
14th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 24, 2026

Last Modified

September 25, 2026

Advisory Details (3)

Auto-updated Sep 25, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
github_commit

commit 20502068902d (pantoniou/libfyaml)

Fix landed in pantoniou/libfyaml commit 20502068902d — awaiting tagged release

https://github.com/pantoniou/libfyaml/commit/20502068902d58c076da873117985798df2c7e74
github_commit

commit 93741a7c9331 (pantoniou/libfyaml)

Fix landed in pantoniou/libfyaml commit 93741a7c9331 — awaiting tagged release

https://github.com/pantoniou/libfyaml/commit/93741a7c9331da9da65ef7a25f2d7d6a817a1c29
generic

[Bug]Stack exhaustion (SIGSEGV) in fy_atom_iter_format() via alloca() growth loop when parsing huge literal/folded block scalars（CWE-770 / CWE-121） · Issue #315 · pantoniou/libfyaml · GitHub

https://github.com/pantoniou/libfyaml/issues/315

Vendor Advisories for CVE-2026-88359(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libfyaml0.7.12-2 ... 0.9.4-1 (7 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libfyaml0.8-1 ... 0.9.4-1 (6 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libfyaml0.8-1 ... 0.9.4-1 (6 versions)
  • every version on: no fix on record
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 17× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-04 20:54 UTCGHSA enrichment
  3. 2026-10-03 20:34 UTCEG score recompute
  4. 2026-10-03 20:34 UTCGHSA enrichment
  5. 2026-10-02 20:14 UTCEG score recompute
  6. 2026-10-02 20:14 UTCGHSA enrichment
  7. 2026-10-01 19:53 UTCEG score recompute
  8. 2026-10-01 19:53 UTCGHSA enrichment
  9. 2026-10-01 19:51 UTCEPSS rescore
  10. 2026-09-30 19:33 UTCEG score recompute
  11. 2026-09-30 19:33 UTCGHSA enrichment
  12. 2026-09-30 15:04 UTCEPSS rescore
  13. 2026-09-29 19:13 UTCEG score recompute
  14. 2026-09-29 19:13 UTCGHSA enrichment
  15. 2026-09-28 18:43 UTCEG score recompute
  16. 2026-09-28 18:43 UTCGHSA enrichment
  17. 2026-09-28 13:52 UTCEPSS rescore
  18. 2026-09-27 18:24 UTCEG score recompute
  19. 2026-09-27 18:24 UTCGHSA enrichment
  20. 2026-09-27 13:48 UTCEPSS rescore
  21. 2026-09-26 18:04 UTCEG score recompute
  22. 2026-09-26 18:04 UTCGHSA enrichment
  23. 2026-09-26 15:59 UTCEPSS rescore
  24. 2026-09-25 17:44 UTCEG score recompute
  25. 2026-09-25 17:44 UTCGHSA enrichment
Show 7 more
  1. 2026-09-25 16:24 UTCEG score recompute▲ 6.50
  2. 2026-09-25 16:24 UTCGHSA enrichment
  3. 2026-09-25 16:24 UTCMITRE cvelistV5CVSS v3 → 6.5 · severity → MEDIUM
  4. 2026-09-24 21:16 UTCGHSA enrichment
  5. 2026-09-24 14:32 UTCNVD update
  6. 2026-09-24 14:17 UTCEG score recompute
  7. 2026-09-24 14:16 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-88359?
CVE-2026-88359 is a medium vulnerability published on September 24, 2026. libfyaml 0.9.6 contains a stack exhaustion vulnerability in fyatomiter_format(). When processing a specially crafted YAML document containing a very large literal or folded block scalar, the function repeatedly grows an internal buffer using alloca() inside a loop. The allocated stack memory is not…
When was CVE-2026-88359 disclosed?
CVE-2026-88359 was first published on September 24, 2026, with the most recent update on September 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-88359 actively exploited?
CVE-2026-88359 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (14th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-88359?
CVE-2026-88359 has a CVSS v3.1 base score of 6.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-88359?
An upstream fix for CVE-2026-88359 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-88359 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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