CVE-2025-8176: LibTIFF Use-After-Free Vulnerability

CVE-2025-8176 Overview

CVE-2025-8176 is a use-after-free vulnerability in LibTIFF versions up to and including 4.7.0. The flaw resides in the get_histogram function in tools/tiffmedian.c, a utility that reduces the color palette of TIFF images. An attacker with local access and low privileges can trigger the use-after-free by supplying a crafted TIFF file to the tiffmedian tool. The issue is tracked under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). Upstream maintainers have released a fix identified by commit fe10872e53efba9cc36c66ac4ab3b41a839d5172.

Critical Impact
Local exploitation of the tiffmedian utility against untrusted TIFF input can corrupt process memory and produce limited confidentiality, integrity, and availability impact.

Affected Products

LibTIFF up to and including version 4.7.0
The tiffmedian command-line utility distributed with LibTIFF
Downstream Linux distributions and applications bundling vulnerable LibTIFF builds

Discovery Timeline

2025-07-26 - CVE-2025-8176 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-8176

Vulnerability Analysis

The vulnerability affects the get_histogram function in tools/tiffmedian.c. This function iterates over image scanlines to build a color histogram used for palette reduction. During processing, a previously freed memory region is dereferenced, producing a use-after-free condition. The upstream project categorizes the issue as memory corruption under [CWE-119].

Exploitation requires local access to invoke tiffmedian against attacker-controlled TIFF data. The attack complexity is low, but privileges are required on the target system. Public disclosure occurred through the LibTIFF GitLab issue tracker and VulDB entry 317590.

Root Cause

The root cause is improper lifetime management of a heap-allocated buffer inside get_histogram. Code paths within tiffmedian.c release the buffer, then continue to reference it during histogram accumulation. The fix landed in commit fe10872e53efba9cc36c66ac4ab3b41a839d5172 via GitLab Merge Request 727, addressing the object lifetime error.

Attack Vector

An attacker must have local access and the ability to run tiffmedian against a crafted TIFF file. Typical exposure scenarios include multi-user systems, batch image conversion pipelines, and automated workflows that invoke tiffmedian on user-supplied files. Successful exploitation may corrupt heap metadata, leak fragments of process memory, or crash the utility.

No verified public exploit code is available. See the GitLab Issue Tracker for the disclosure discussion and the Commit Update for the patched source.

Detection Methods for CVE-2025-8176

Indicators of Compromise

Unexpected crashes or SIGSEGV terminations of the tiffmedian process on hosts that process TIFF files
Anomalous invocations of tiffmedian against files sourced from untrusted directories or upload paths
Heap corruption warnings from AddressSanitizer or glibc malloc diagnostics referencing get_histogram

Detection Strategies

Inventory all systems with LibTIFF installed and identify installed versions using package managers such as dpkg -l libtiff* or rpm -q libtiff
Monitor process execution telemetry for tiffmedian invocations, correlating command-line arguments with file provenance
Deploy runtime memory safety instrumentation (AddressSanitizer, Valgrind) in development and QA environments that consume LibTIFF

Monitoring Recommendations

Alert on tiffmedian process crashes recorded in /var/log/syslog, journalctl, or Windows Event Log
Track file-open events for .tif and .tiff files from world-writable or upload directories
Capture core dumps for post-mortem analysis when LibTIFF tools terminate abnormally

How to Mitigate CVE-2025-8176

Immediate Actions Required

Apply the upstream patch commit fe10872e53efba9cc36c66ac4ab3b41a839d5172 or upgrade to a LibTIFF release incorporating the fix
Restrict execution of tiffmedian to trusted users and validated input paths
Rebuild and redistribute any downstream packages, containers, or images that bundle the vulnerable LibTIFF source

Patch Information

The fix is committed to the LibTIFF upstream repository. Review the GitLab Commit Update and the associated GitLab Merge Request 727 for source-level changes. Distribution maintainers should backport the commit to any supported branch shipping LibTIFF 4.7.0 or earlier.

Workarounds

Avoid running tiffmedian on untrusted TIFF input until the patch is applied
Execute tiffmedian inside a sandbox such as firejail, bubblewrap, or a container with a read-only filesystem
Remove or restrict permissions on the tiffmedian binary on systems where color palette reduction is not required

bash

# Configuration example
# Verify installed LibTIFF version
tiffinfo -v 2>&1 | head -n 1

# Restrict tiffmedian execution to a trusted group
sudo chgrp trusted-imaging /usr/bin/tiffmedian
sudo chmod 750 /usr/bin/tiffmedian

# Optional: run tiffmedian under a sandbox
firejail --net=none --private-tmp tiffmedian input.tif output.tif