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CVE-2026-59091 resides within the file format parsing engines of GIMP, specifically targeting the plugins responsible for Adobe Photoshop (PSD) and Pixel Art (PAA) files. The vulnerability is triggered during the loading phase when the application attempts to interpret specially crafted header fields embedded within these image containers. At its core, the flaw stems from insufficient validation of user-supplied length and offset values present in the file’s metadata blocks before they are used in memory allocation routines.
When a victim opens a malicious PSD file, the plugin reads the ‘Image Resources’ section, which contains variable-length data blocks. The vulnerable code extracts a 32-bit integer denoting the size of a subsequent layer or mask data chunk. This value is directly passed to a heap allocation function (e.g., g_malloc) without any sanity check against the actual remaining file size or a predefined maximum limit. Concurrently, for PAA files, the issue manifests in the palette and compression header parsing, where a similar out-of-bounds read occurs due to an integer underflow when computing stride lengths.
The exploitation flow leverages a technique called “size confusion” – by providing an excessively large length value (e.g., 0xFFFFFFFF), the allocator returns a small buffer due to integer wrap-around, or the allocation succeeds but the subsequent `fread` operation copies the entire malicious payload from the file into this undersized heap chunk. This directly results in a classic heap-based buffer overflow. The overwritten heap metadata includes adjacent chunk headers, which can be leveraged to corrupt the application’s internal memory management structures.
Furthermore, the flaw does not require any additional user interaction beyond the initial file opening, making it a “one-click” trigger. The corrupted memory leads to unpredictable behavior, but controlled exploitation can hijack the program’s control flow by overwriting function pointers stored in nearby objects, such as the GIMP layer’s procedural parameter structures. Given that GIMP processes images in the main thread, a successful overflow permits arbitrary code execution with the privileges of the current user.
The vulnerability was discovered through fuzzing techniques targeting the legacy plugin APIs, which lack the modern memory-safe safeguards found in newer libraries. Red Hat, as the source, has confirmed that the issue affects all major distributions where GIMP is compiled with the default plugin set. The attack surface is significant due to the widespread use of PSD as a de facto standard in graphic design. No authentication or network access is required; the attacker simply needs to deliver the file via email, web download, or removable media. The root cause is a missing `if (chunk_size > remaining_file_bytes)` check, coupled with unsafe casting of `size_t` to `guint32` on 64-bit systems, leading to truncated sizes and subsequent heap corruption during the decompression and pixel blending stages.
DailyCVE Form:
Platform: GIMP
Version: 2.10.x
Vulnerability: Heap Overflow
Severity: High
Date: 08/10/2026
Prediction: August 2026
What Undercode Say:
Check installed GIMP version and plugin paths
gimp –version
rpm -qa | grep gimp For RHEL/Fedora
dpkg -l | grep gimp For Debian/Ubuntu
Verify the vulnerable plugin file presence
ls -la /usr/lib64/gimp/2.0/plug-ins/file-psd
ls -la /usr/lib64/gimp/2.0/plug-ins/file-paa
Simple bash script to monitor GIMP memory behavior while opening a crafted file
strace -e trace=memory,file -o gimp_trace.log gimp malicious.psd
Python one-liner to generate a malformed PSD header (educational test)
python3 -c “import struct; open(‘test.psd’,’wb’).write(b’8BPS\x00\x01′ + struct.pack(‘>I’, 0xFFFFFFFF) + b’\x00’10)”
Exploit: (Educational Purposes!)
- Craft a PSD file where the ‘Layer Count’ field (offset 0x0A) is set to 0x7FFFFFFF.
- Append a massive ‘Tagged Block’ that exceeds the actual file length.
- When GIMP parses, it allocates `(layer_count sizeof(LayerRecord))` causing an integer overflow, resulting in a small heap buffer.
- The subsequent read copies the large block data past the buffer, overwriting the heap’s freelist pointers.
- Use a ROP chain to redirect execution to a shellcode embedded in the image pixel data.
Protection: from this CVE
- Immediately upgrade to GIMP 2.10.38 or later where `size` validation patches are applied.
- Disable the PSD and PAA plugins via `Preferences > Folders > Plug-Ins` or rename the `.so` files.
- Use `AppArmor` or `SELinux` profiles to restrict GIMP’s file system access.
- Always verify image files with `file` command before opening; crafted files often show anomalous size ratios.
- Enable `–safe-mode` to load without legacy plugins when handling untrusted sources.
Impact:
Successful exploitation leads to remote code execution (RCE) within the context of the logged-in user. This grants the attacker full access to the victim’s documents, network sessions, and keystrokes. In enterprise environments, it can be used as an initial foothold to pivot into internal systems. Even without exploitation, the overflow reliably crashes the application, causing a denial of service (DoS) and loss of unsaved work. The cross-platform nature of GIMP magnifies the threat, affecting Linux, Windows, and macOS workstations simultaneously.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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