CVE-2026-6694: GIMP file-png Plugin DoS Vulnerability

CVE-2026-6694 Overview

CVE-2026-6694 is a stack-based buffer overflow vulnerability in the file-png plugin of GIMP, the GNU Image Manipulation Program. The flaw stems from improper handling of an oversized tRNS chunk in Animated Portable Network Graphics (APNG) images. When a user opens a crafted APNG file, the plugin writes past a fixed-size stack buffer and crashes. The condition is tracked under CWE-120 (Buffer Copy without Checking Size of Input), and the impact is limited to Denial of Service (DoS) against the GIMP process.

Critical Impact
A remote attacker can crash the GIMP file-png plugin by delivering a malicious APNG file, resulting in Denial of Service when the user opens the image.

Affected Products

GIMP file-png plugin (per Red Hat CVE-2026-6694 Advisory)
Specific fixed versions: Not Available
Distribution packages: See Red Hat Bug Report #2459779

Discovery Timeline

2026-08-03 - CVE-2026-6694 published to NVD
2026-08-03 - Last updated in NVD database

Technical Details for CVE-2026-6694

Vulnerability Analysis

The vulnerability resides in the GIMP file-png plugin, which parses PNG and APNG image data on file open. The APNG format extends PNG with animation chunks, and the tRNS chunk carries transparency data associated with the palette or color type. The plugin allocates a fixed-size stack buffer to hold tRNS entries. It does not validate the declared chunk length against that buffer size before copying data. A crafted APNG with an oversized tRNS chunk overruns the stack buffer, corrupting adjacent stack memory and crashing the plugin.

Exploitation requires user interaction. A victim must open the malicious file in GIMP, either directly or through a file manager preview that invokes the plugin. The impact is limited to availability. The advisory does not describe conditions leading to arbitrary code execution, and the CWE classification aligns with a classic bounds-check omission rather than a controlled write primitive.

Root Cause

The root cause is missing input validation on the length field of the tRNS chunk before data is written into a stack-resident buffer inside the file-png plugin. The parser trusts the attacker-controlled chunk length, which enables the overflow described in CWE-120.

Attack Vector

The attack vector is local and requires user interaction. An attacker distributes a crafted APNG file through email, web download, shared storage, or a chat channel. When the user opens the file in GIMP, the file-png plugin parses the malformed tRNS chunk and crashes. No authentication is required on the target system. Confidentiality and integrity are not impacted; availability of the GIMP process is lost.

No verified exploit code is available for this issue. See the Red Hat CVE-2026-6694 Advisory and Red Hat Bug Report #2459779 for parser-level details.

Detection Methods for CVE-2026-6694

Indicators of Compromise

Unexpected crashes of the GIMP file-png plugin or the parent gimp process shortly after opening an image file.
Core dumps or crash reports referencing the file-png plugin binary in system journals (journalctl, abrt, systemd-coredump).
APNG or PNG files from untrusted sources containing a tRNS chunk whose declared length exceeds standard palette bounds (256 bytes).

Detection Strategies

Inspect PNG and APNG files at ingress with a parser that validates chunk lengths against expected maximums for tRNS and rejects malformed inputs.
Correlate endpoint process termination events for gimp and its plugin processes with recent file-open activity on image files.
Alert on repeated crashes of the same image-processing binary across multiple hosts, which can indicate a common malicious payload in circulation.

Monitoring Recommendations

Forward Linux coredump and abrt events, along with process termination telemetry, to a central SIEM for correlation with file download and email delivery events.
Track downloads and email attachments with .png and .apng extensions from untrusted senders and flag repeat crashes on hosts that opened them.
Baseline normal GIMP process lifecycles per user and alert on abnormal termination patterns tied to image-handling plugins.

How to Mitigate CVE-2026-6694

Immediate Actions Required

Apply vendor updates for GIMP once distributions publish patched packages. Track status on the Red Hat CVE-2026-6694 Advisory.
Instruct users not to open PNG or APNG files received from untrusted sources until the update is applied.
Inventory endpoints and build servers that run GIMP or invoke its plugins in automated pipelines and prioritize them for patching.

Patch Information

Red Hat tracks the fix under Bug #2459779. Fixed package versions were not listed in the NVD entry at the time of publication. Consult your Linux distribution's security tracker for the specific GIMP package version that addresses CVE-2026-6694.

Workarounds

Disable or remove the file-png plugin from GIMP installations where PNG editing is not required, until a patched version is installed.
Route inbound PNG and APNG attachments through a sanitizing gateway that re-encodes images and strips non-standard chunks.
Open untrusted image files inside a sandboxed environment such as a disposable container or a virtual machine to contain crashes and limit exposure.

bash

# Example: check installed GIMP version and query the distribution security tracker
gimp --version

# Debian/Ubuntu
apt policy gimp

# Red Hat / Fedora
rpm -q gimp
dnf updateinfo info --cve CVE-2026-6694