---
id: CVE-2026-88359
title: >-
  libfyaml 0.9.6 contains a stack exhaustion vulnerability in
  fy_atom_iter_format()
summary: >-
  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…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
vendor: Red Hat
published: '2026-09-24'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T17:17:17.490'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88359'
references:
  - url: >-
      https://github.com/pantoniou/libfyaml/commit/20502068902d58c076da873117985798df2c7e74
    label: cve@mitre.org
  - url: >-
      https://github.com/pantoniou/libfyaml/commit/93741a7c9331da9da65ef7a25f2d7d6a817a1c29
    label: cve@mitre.org
  - url: 'https://github.com/pantoniou/libfyaml/issues/315'
    label: cve@mitre.org
  - url: 'https://github.com/pantoniou/libfyaml/issues/315'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-88359.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-88359'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-88359'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-25T16:18:24.616054Z'
scores:
  nvd: 6.5
  vendor: 6.2
  adp: 6.5
ingestedAt: '2026-09-24T14:44:21.326Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-88359.json)