---
id: CVE-2026-120251
title: imagecodecs 2026.3.6 through 2026.10.10 Infinite Loop via ccittfax4_decode()
summary: >-
  imagecodecs 2026.3.6 through 2026.10.10 contains an infinite loop
  vulnerability in ccitt_fax4_decode_size() that allows attackers to hang the
  calling process by supplying a crafted CCITT Group 4 stream. Attackers can
  provide an 8-byte G4…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-835
vendor: cgohlke
product: imagecodecs
affected:
  - imagecodecs >= 2026.3.6 <= 2026.10.10
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T18:56:56.662592Z'
exploitAvailable: true
published: '2026-11-01'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T18:57:26.486Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-120251'
references:
  - url: 'https://github.com/cgohlke/imagecodecs/issues/158'
    label: 'GitHub Issue #158'
  - url: >-
      https://github.com/cgohlke/imagecodecs/blob/v2026.10.10/3rdparty/ccitt/ccitt.c#L1449
  - url: 'https://github.com/cgohlke/imagecodecs'
  - url: >-
      https://www.vulncheck.com/advisories/imagecodecs-2026.3.6-through-2026.10.10-infinite-loop-via-ccittfax4-decode
    label: >-
      VulnCheck Advisory: imagecodecs 2026.3.6 through 2026.10.10 Infinite Loop
      via ccittfax4_decode()
tags:
  - cve.org
  - exploit-available
epss: 0.00124
epssPercentile: 0.02133
ingestedAt: '2026-11-05T18:28:50.670Z'
---

## Overview

imagecodecs 2026.3.6 through 2026.10.10 contains an infinite loop vulnerability in ccitt_fax4_decode_size() that allows attackers to hang the calling process by supplying a crafted CCITT Group 4 stream. Attackers can provide an 8-byte G4 stream lacking EOFB to ccittfax4_decode() or the numcodecs Ccittfax4 codec, consuming full CPU until the process is killed.

## Affected

- `imagecodecs >= 2026.3.6 <= 2026.10.10`

## Remediation

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