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Fencer Vulns
medium 5.5

CVE-2026-56289 json

Loop with Unreachable Exit Condition in GNU patch

published 2026-07-09 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-42557 , GHSA-3m3r-f94v-4mf8 , JLSEC-2026-1261

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

GNU patch is vulnerable to a denial of service (DoS) due to improper validation of hunk (single block of changes in diff) line offsets in unified-diff input. A specially crafted patch can specify an extremely large line number, causing the application to enter an effectively infinite processing loop while attempting to locate the requested position. This results in excessive CPU consumption and prevents the process from completing. An attacker can trigger this behavior by supplying a malicious patch file, causing the utility to become unresponsive and require manual termination.

This issue has been fixed in the commit faba04ef4f2b410257f76c1b9dc85e350929c4b9

Patch / fix

  • patch hummingbird 1 2.8-4.2.hum1

red hat advisories RHSA-2026:37468

  • patch Linux Micro 6.0 2.7.6-4.1
  • patch Linux Micro 6.1 2.7.6-slfo.1.1_2.1
  • patch SLE Module for Basesystem 15 SP7 2.7.6-150000.5.12.1
  • patch SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.7.6-160000.4.1
  • patch SLES LTSS Extended Security 12 SP5 2.7.5-8.14.1

suse advisories SUSE-SU-2026:23210-1SUSE-SU-2026:22905-1SUSE-SU-2026:3161-1SUSE-SU-2026:22604-1SUSE-SU-2026:22651-1SUSE-SU-2026:2922-1

  • patch openSUSE Leap 16.0 2.7.6-160000.4.1
  • patch openSUSE Tumbleweed 2.8-3.1

opensuse advisories openSUSE-SU-2026:21332-1openSUSE-SU-2026:11260-1

  • patch Alpine 3.24 2.8.1-r0

alpine advisories ALPINE-CVE-2026-56289

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • patch Azure Linux 3.0 2.7.6-10

azure linux advisories AZL-92151

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-56289 updated cvss 5.5

patch: GNU patch: Denial of Service via crafted unified-diff input

  • Red Hat Hardened Images patch 2.8-4.2.hum1
    fixed: vendor fix RHSA-2026:37468

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.11% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 4.6 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
CNA 4.0 4.6 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
julia patch_jll
all versions
 no fix listed

Affected products

  • GNU patch

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.