CVE-2026-8454: Tonyc Imager Buffer Overflow Vulnerability

CVE-2026-8454 Overview

CVE-2026-8454 is a heap out-of-bounds write vulnerability in Imager::File::GIF versions through 1.002 for Perl. The flaw resides in the i_readgif_multi_low function, which allocates a single per-row GifRow buffer sized to the GIF's global screen width (SWidth) and reuses it across every image frame in the file. While the page-match branch validates Image.Width + Image.Left > SWidth before each DGifGetLine write, the parallel skip-image branch at imgif.c:790-805 performs no such bounds check. Attackers can craft multi-frame GIF files that trigger the unchecked write path, corrupting heap memory during image decoding [CWE-787].

Critical Impact
Processing a crafted multi-frame GIF in any Perl application using Imager::File::GIF causes a heap out-of-bounds write, potentially leading to memory corruption, crashes, or arbitrary code execution.

Affected Products

Tonyc Imager::File::GIF for Perl, all versions through 1.002
Perl applications that consume untrusted GIF input via the Imager module
Downstream Linux distributions packaging Imager-File-GIF ≤ 1.002

Discovery Timeline

2026-05-15 - Vulnerability disclosed via OpenWall oss-security mailing list
2026-05-15 - CVE-2026-8454 published to NVD
2026-05-18 - Last updated in NVD database

Technical Details for CVE-2026-8454

Vulnerability Analysis

The vulnerability resides in i_readgif_multi_low inside imgif.c, the core multi-frame GIF reader for Imager::File::GIF. The function allocates one GifRow buffer of length SWidth (the GIF global screen width) once and reuses it for every embedded image. Each sub-image within a GIF can declare its own Image.Width and Image.Left offsets in its local image descriptor. When a frame's Image.Width + Image.Left exceeds SWidth, writing a row of that frame into GifRow overflows the heap allocation.

Root Cause

The page-match decoding branch correctly checks Image.Width + Image.Left > SWidth and rejects frames that would write past the buffer. The parallel skip-image branch at imgif.c:790-805 calls DGifGetLine(GifFile, GifRow, Width) using the attacker-controlled local Width value without performing the equivalent validation. This inconsistency between the two code paths allows oversized rows to be written into a fixed-size heap buffer [CWE-787].

Attack Vector

Exploitation requires the victim to open or otherwise process a malicious GIF file with an application that uses Imager::File::GIF. The attacker crafts a multi-frame GIF whose secondary frames declare Width and Left values that sum beyond the file's declared SWidth. When the decoder reaches the skip-image branch, DGifGetLine writes beyond GifRow, corrupting adjacent heap memory. User interaction is required to supply the malicious file.

text

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

Source: GitHub Patch Commit

The upstream patch adds the missing width and offset validation to the skip-image branch, aligning it with the page-match branch.

Detection Methods for CVE-2026-8454

Indicators of Compromise

Perl processes linking Imager::File::GIF crashing with SIGSEGV or glibc heap corruption messages such as malloc(): corrupted chunk while parsing GIF input
GIF files where sub-image local descriptors declare Image.Width + Image.Left greater than the file's Logical Screen Width
Unexpected child process termination in image-processing pipelines (CMS uploads, thumbnailers, mail filters) when handling user-supplied GIFs

Detection Strategies

Inspect installed Perl module versions and flag any host with Imager::File::GIF ≤ 1.002 using cpan -D Imager::File::GIF or distribution package queries
Statically scan inbound GIF files for malformed frame geometry by parsing the Logical Screen Descriptor and each Image Descriptor before passing them to vulnerable decoders
Monitor application logs and core dumps from web services, mail gateways, and batch jobs that process attacker-controlled GIFs

Monitoring Recommendations

Forward Perl application crash telemetry and coredumpctl events into a centralized log platform for correlation against image upload activity
Track outbound network connections initiated by image-processing workers immediately after GIF parsing to surface post-exploitation behavior
Alert on repeated GIF parse failures from a single source, which can indicate fuzzing or exploit reconnaissance

How to Mitigate CVE-2026-8454

Immediate Actions Required

Upgrade Imager::File::GIF to version 1.003 or later on every host that runs Perl-based image processing
Audit dependent applications (web apps, mailers, asset pipelines) for direct or transitive use of Imager::File::GIF and schedule restarts after upgrade
Until patching completes, reject or pre-validate untrusted GIF uploads using a standalone parser that enforces Image.Width + Image.Left <= SWidth

Patch Information

The vendor fixed the issue in Imager-File-GIF 1.003, released alongside Imager 1.030 on 13 Apr 2026. The fix commit 782e9c06cc75a0f7eed383f39522f51f44598b04 adds bounds validation to the skip-image branch in imgif.c. See the GitHub Patch Commit and the MetaCPAN Release Changes for details. Additional context is available in the OpenWall OSS-Security Post.

Workarounds

Disable GIF processing in Imager workflows where feasible by restricting accepted formats to PNG or JPEG until the patched module is deployed
Sandbox Perl image-processing workers with seccomp, AppArmor, or container isolation to limit the impact of heap corruption
Pre-filter GIF inputs through a hardened tool such as ImageMagick with strict policy.xml limits before handing files to Imager

bash

# Upgrade Imager::File::GIF to the patched release
cpanm Imager::File::GIF@1.003

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