CVE-2026-8669: Perl Imager Buffer Overflow Vulnerability

CVE-2026-8669 Overview

CVE-2026-8669 is a heap out-of-bounds write vulnerability in the Imager module for Perl, affecting versions through 1.030. The flaw resides in Imager::File::GIF's i_readgif_multi_low function, which processes multi-frame GIF files. A single per-row buffer named GifRow is allocated based on the GIF's global screen width (SWidth) and reused across every image frame in the file. While the page-match branch validates frame dimensions before writes, the parallel skip-image branch at imgif.c:790-805 calls DGifGetLine(GifFile, GifRow, Width) without bounds checking. Attackers can craft malicious GIF files to trigger memory corruption in applications that process untrusted images using Imager.

Critical Impact
Crafted multi-frame GIF files trigger heap out-of-bounds writes in any Perl application using Imager to parse untrusted GIF input, potentially leading to memory corruption and information disclosure.

Affected Products

Imager module for Perl, versions through 1.030
Imager-File-GIF versions through 1.002
Perl applications and web services that process untrusted GIF images via Imager

Discovery Timeline

2026-05-15 - CVE-2026-8669 published to NVD
2026-05-15 - Disclosure posted to OpenWall OSS-Security mailing list
2026-05-18 - Last updated in NVD database

Technical Details for CVE-2026-8669

Vulnerability Analysis

The vulnerability is classified as an out-of-bounds write [CWE-787] in the GIF decoder of the Imager Perl module. Imager is widely used in Perl-based image processing pipelines, including web applications that accept user-uploaded images. The flaw allows a remote attacker to corrupt heap memory by submitting a crafted multi-frame GIF file. Successful exploitation can cause process crashes, information disclosure, or potentially influence application behavior depending on heap layout.

Root Cause

The root cause is inconsistent bounds validation between two code paths that share a single row buffer. The i_readgif_multi_low function allocates GifRow once, sized to the GIF's global screen width SWidth. The page-match branch correctly validates that Image.Width + Image.Left > SWidth before each call to DGifGetLine. The parallel skip-image branch at imgif.c:790-805 omits this check entirely and calls DGifGetLine(GifFile, GifRow, Width) directly. When a frame's Width exceeds SWidth, the libgif decoder writes past the end of GifRow on the heap.

Attack Vector

Exploitation requires the attacker to supply a crafted GIF file to an application that uses Imager for decoding. No authentication or user interaction beyond image processing is required. The attack surface includes web upload handlers, mail processors, and any service that parses GIF data through Imager. The patch addressing this issue was committed upstream by the Imager maintainer.

text

+ - GIF: fix a heap buffer overflow with attacker controlled data
+   CVE-2026-8454
+
 Imager 1.030 - 13 Apr 2026
 ============

Source: GitHub Patch Commit

text

+Imager-File-GIF 1.003
+=====================
+
+ - fix a buffer overflow when reading images
+   CVE-2026-8454
+
 Imager-File-GIF 1.002

Source: MetaCPAN Release Changes

Note: The upstream changelog references CVE-2026-8454 as the original identifier associated with the fix commit. CVE-2026-8669 covers the same i_readgif_multi_low skip-image branch defect.

Detection Methods for CVE-2026-8669

Indicators of Compromise

Process crashes or segmentation faults in Perl workers handling GIF uploads
Heap corruption errors logged by glibc or address sanitizer when Imager::File::GIF is in the call stack
Inbound multi-frame GIF files where individual frame Width + Left exceeds the declared SWidth of the screen descriptor

Detection Strategies

Inventory Perl environments to identify installations of Imager and Imager::File::GIF with versions at or below 1.030 and 1.002 respectively
Inspect GIF uploads for anomalies in the Logical Screen Descriptor and per-frame Image Descriptor dimensions before passing files to Imager
Enable address sanitizer or heap-protection instrumentation in pre-production environments to catch out-of-bounds writes during fuzz testing

Monitoring Recommendations

Monitor application logs for repeated abnormal termination of Perl processes that handle image decoding
Track outbound and inter-service traffic from image-processing workers for unexpected behavior following GIF parsing
Alert on web upload endpoints receiving GIF files significantly larger or more complex than typical user-generated content

How to Mitigate CVE-2026-8669

Immediate Actions Required

Upgrade Imager to version 1.031 or later and Imager::File::GIF to version 1.003 or later from CPAN
Audit all Perl applications and services for direct or transitive dependencies on Imager
Restrict or sandbox image-processing workers that handle untrusted GIF input until patches are deployed

Patch Information

The fix is available in Imager 1.031, published on MetaCPAN. The upstream commit 782e9c06cc75a0f7eed383f39522f51f44598b04 adds the missing bounds check on the skip-image branch in imgif.c. Review the GitHub Patch Commit and the MetaCPAN Release Changes for full details. Additional context is available in the OpenWall OSS-Security Post.

Workarounds

Reject GIF uploads at the application boundary until Imager is updated, or convert images using an alternate decoder such as ImageMagick or libvips
Pre-validate GIF headers in a separate process to reject files where any frame's Image.Width + Image.Left exceeds the global SWidth
Run Imager-based decoders inside isolated containers or seccomp-restricted processes to limit the impact of memory corruption

bash

# Upgrade Imager and the GIF backend via CPAN
cpanm Imager@1.031
cpanm Imager::File::GIF@1.003

# Verify installed versions
perl -MImager -e 'print $Imager::VERSION, "\n"'
perl -MImager::File::GIF -e 'print $Imager::File::GIF::VERSION, "\n"'