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TI-2026-83576 Aliases CVE-2026-120251GHSA-j736-6c4x-7rx7

Infinite loop in imagecodecs CCITT Group 4 decoder

Priority MEDIUM 63CWE-835Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
Passive
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-835.

Summary

The imagecodecs package from cgohlke, versions 2026.3.6 through 2026.10.10, contains an infinite loop in ccitt_fax4_decode_size() (CWE-835). A crafted CCITT Group 4 stream that lacks an end-of-block marker causes the decoder to loop forever. An unauthenticated attacker who can supply input to ccittfax4_decode() or the numcodecs Ccittfax4 codec can hang the calling process at full CPU use until it is killed, and a user must interact with the application for this to occur.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00124 2nd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
cgohlkeimagecodecs2026.3.6 – 2026.10.10—No fix listedCNA
  • imagecodecs Vendorcgohlke Affected 2026.3.6 – 2026.10.10 Fixed in — No fix listed CNA

Remediation

The sources list no fixed version for imagecodecs.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-11-01 Threatist record created from CVE-2026-120251
  2. 2026-11-01 Alias added: GHSA-j736-6c4x-7rx7
  3. 2026-11-02 Priority changed: MEDIUM → LOW
  4. 2026-11-02 Affected versions changed · Red Hat
  5. 2026-11-02 CVSS score added · Red Hat
  6. 2026-11-06 CISA SSVC decision points changed
  7. 2026-11-06 Priority changed: LOW → MEDIUM

References

Other 3

  • TI-2026-83577 imagecodecs Stack Buffer Overflow via jpegsof3_decode() CVSS 4.0MEDIUM 6.8

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences