CVE-2026-42170 Overview
CVE-2026-42170 is a heap-based buffer overflow in the GNU Image Manipulation Program (GIMP) DirectDraw Surface (DDS) file parser. The vulnerability stems from an incorrect buffer size calculation when a crafted DDS file declares a Direct3D 9 (D3D9) pixel format but reports a smaller bits-per-pixel (bpp) value in its header. The loader allocates an undersized heap buffer based on the declared bpp. Pixel data is then consumed at the real format's stride, causing writes past the heap buffer boundary. The result is heap metadata corruption and potential arbitrary code execution under the context of the user running GIMP.
Critical Impact
A crafted DDS file opened in GIMP can corrupt heap metadata and enable local code execution with the privileges of the invoking user.
Affected Products
- GNU Image Manipulation Program (GIMP) DDS file plug-in
- Linux distributions shipping vulnerable GIMP builds (see Red Hat advisory)
- Applications embedding the GIMP DDS parser
Discovery Timeline
- 2026-08-08 - CVE-2026-42170 published to the National Vulnerability Database (NVD)
- 2026-08-11 - Last updated in the NVD database
Technical Details for CVE-2026-42170
Vulnerability Analysis
The flaw resides in the DDS loader path used by GIMP to import DirectDraw Surface textures. DDS files carry a header describing width, height, pixel format, and bpp. The loader trusts the header's bpp field when computing the allocation size for the pixel buffer. When the header declares a D3D9 pixel format such as D3DFMT_A8R8G8B8 (32 bpp) but reports a lower bpp value, the allocation is sized for the smaller value while the decode path reads pixels at the true format stride.
The write loop overruns the allocation and clobbers adjacent heap metadata. This condition maps to [CWE-131] Incorrect Calculation of Buffer Size. Because the write is attacker-controlled, adversaries can craft DDS files that steer heap layout to gain arbitrary write primitives and, ultimately, code execution.
Root Cause
The parser derives buffer size from the untrusted bpp header field rather than from the canonical stride of the declared pixel format. The mismatch between the allocated size and the decode-time stride creates an out-of-bounds write on every scanline processed beyond the allocation boundary.
Attack Vector
Exploitation requires user interaction. A victim must open or preview a malicious .dds file in GIMP. The attack vector is local, with no privileges required beyond the ability to place a file where the user will open it. Common delivery paths include email attachments, shared network drives, and archives extracted for asset inspection. Refer to the Red Hat CVE-2026-42170 Advisory and Red Hat Bug Report #2461726 for vendor tracking details.
Detection Methods for CVE-2026-42170
Indicators of Compromise
- GIMP process crashes or SIGABRT events referencing heap corruption shortly after opening a .dds file
- Unexpected child processes spawned from the GIMP process tree following image import
- .dds files whose header-declared bpp does not match the canonical bpp of the declared D3D9 pixel format
Detection Strategies
- Deploy YARA or file-classification rules that parse DDS headers and flag bpp mismatches against the declared dwFourCC or pixel format mask
- Enable AddressSanitizer (ASan) or glibc MALLOC_CHECK_ in test environments to surface the overflow deterministically
- Correlate GIMP crash telemetry with recent file-open events on workstations used by design and asset teams
Monitoring Recommendations
- Alert on GIMP spawning shells, scripting interpreters, or network utilities such as bash, python, or curl
- Monitor endpoints for .dds files arriving via email gateways, browser downloads, or removable media
- Track GIMP version inventory across Linux, macOS, and Windows workstations to identify unpatched hosts
How to Mitigate CVE-2026-42170
Immediate Actions Required
- Apply vendor-supplied GIMP updates from your distribution as soon as they are released for CVE-2026-42170
- Restrict opening of untrusted .dds files until patched builds are deployed
- Communicate the risk to graphic design, game development, and 3D asset teams that routinely process DDS textures
Patch Information
At publication, distribution patches are tracked through the Red Hat CVE-2026-42170 Advisory. Monitor upstream GIMP release notes and your Linux distribution's security channels for the fixed package version. Windows and macOS users should update to the next GIMP release incorporating the DDS parser fix.
Workarounds
- Disable or remove the GIMP DDS plug-in binary from the plug-ins directory if DDS support is not required
- Open untrusted DDS files only inside a sandboxed environment such as Firejail, Flatpak, or a disposable virtual machine
- Enforce file-type policies at the email and web gateway to block or quarantine inbound .dds attachments
- Run GIMP under a non-privileged account with mandatory access controls such as SELinux or AppArmor in enforcing mode
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
