Bug 2448747 (CVE-2026-26740)

Summary: CVE-2026-26740 giflib: giflib: Denial of Service via buffer overflow in EGifGCBToExtension
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: ahughes, caryn.ciampa, fferrari, khosford, mtorre, pjindal, rhel-process-autobot, tfitzsim, tosorio, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in giflib. A remote attacker can exploit a buffer overflow vulnerability in the EGifGCBToExtension function by providing a specially crafted Graphics Control Extension (GCE) block. This allows overwriting an existing GCE block without proper size validation, leading to a denial of service (DoS) on the system.
Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2448828, 2448829, 2448831, 2448832, 2448833, 2448834, 2448835, 2448836, 2448830    
Bug Blocks:    

Description OSIDB Bzimport 2026-03-18 19:03:00 UTC
Buffer Overflow vulnerability in giflib v.5.2.2 allows a remote attacker to cause a denial of service via the EGifGCBToExtension overwriting an existing Graphic Control Extension block without validating its allocated size.

Comment 2 Thiago Osório 2026-05-27 17:43:11 UTC
Hi, team. I hope you're doing well. 

  Do we have an ETA for the fix for this CVE-2026-26740 vulnerability to the Red Hat build of OpenJDK 21 (java-21-openjdk-portable)?

  Regards.

Comment 3 Francisco Ferrari Bihurriet 2026-05-27 22:31:59 UTC
Hi,

Here is a public disclosure of the issue:
  https://github.com/zakkanijia/POC/blob/main/giflib/giftool/giflib_giftool_gce_len_heap_oobwrite_disclosure.md

The affected components are the EGifGCBToExtension and EGifGCBToSavedExtension functions, implemented in egif_lib.c:
  https://sourceforge.net/p/giflib/code/ci/6.1.3/tree/egif_lib.c#l658
  https://sourceforge.net/p/giflib/code/ci/6.1.3/tree/egif_lib.c#l675

This is not resolved in GifLib upstream yet, probably addressed by one of the patches attached to the following issues:
  GifLib bug #​199: Buffer Overflow vulnerability in giflib
  https://sourceforge.net/p/giflib/bugs/199/
  GifLib bug #​201: Heap buffer overflow in EGifGCBToSavedExtension on malformed Graphics Control Extension
  https://sourceforge.net/p/giflib/bugs/201/

Here is a discussion with the maintainers, where they mention a fix is in the pipeline:
  https://sourceforge.net/p/giflib/mailman/giflib-devel/thread/SAWPR05MB99856275F12A2F9834E58B8CE9B356A%40SAWPR05MB998562.namprd05.prod.outlook.com/#msg59313739

However, OpenJDK sources do not include egif_lib.c, and the only occurrences of these functions in OpenJDK code are their declarations in gif_lib.h:
  https://github.com/openjdk/jdk/blob/jdk-27+22/src/java.desktop/share/native/libsplashscreen/giflib/gif_lib.h#L282-L283
  https://github.com/openjdk/jdk/blob/jdk-27+22/src/java.desktop/share/native/libsplashscreen/giflib/gif_lib.h#L287-L288

Thus, to my understanding, none of the OpenJDK versions are affected by CVE-2026-26740, because they do NOT ship the vulnerable code.

Comment 4 errata-xmlrpc 2026-06-30 09:37:21 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:33447 https://access.redhat.com/errata/RHSA-2026:33447

Comment 5 errata-xmlrpc 2026-06-30 10:02:25 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:33450 https://access.redhat.com/errata/RHSA-2026:33450

Comment 6 errata-xmlrpc 2026-06-30 10:07:25 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:33451 https://access.redhat.com/errata/RHSA-2026:33451

Comment 7 errata-xmlrpc 2026-06-30 10:24:40 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:33455 https://access.redhat.com/errata/RHSA-2026:33455

Comment 8 errata-xmlrpc 2026-06-30 10:30:46 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:33452 https://access.redhat.com/errata/RHSA-2026:33452

Comment 9 errata-xmlrpc 2026-06-30 10:46:31 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:33456 https://access.redhat.com/errata/RHSA-2026:33456

Comment 10 errata-xmlrpc 2026-06-30 13:59:03 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:33509 https://access.redhat.com/errata/RHSA-2026:33509

Comment 11 errata-xmlrpc 2026-06-30 14:24:04 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:33503 https://access.redhat.com/errata/RHSA-2026:33503

Comment 12 errata-xmlrpc 2026-06-30 22:55:44 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:33502 https://access.redhat.com/errata/RHSA-2026:33502

Comment 13 errata-xmlrpc 2026-06-30 23:31:48 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:33501 https://access.redhat.com/errata/RHSA-2026:33501