CVE-2026-78465: Integer Overflow or Wraparound in GNOME GIMP

The vulnerability in GIMP's file-pcx plugin affects 32-bit builds only. When processing PCX files, the plugin calculates memory allocation sizes based on image dimensions and color planes. If a crafted PCX file sets the number of planes to 4 with sufficiently large dimensions, the calculation overflows a 32-bit integer, causing an undersized heap buffer allocation. Writing image data into this undersized buffer triggers a heap-based buffer overflow, leading to memory corruption. This can potentially allow arbitrary code execution or denial of service. Exploitation requires convincing a user to open a malicious PCX file locally. Red Hat's advisory notes that default security mechanisms increase exploitation difficulty and rates the severity as important (high). No patch or remediation level is currently stated in the advisory.

The integer overflow causes a heap-based buffer overflow, resulting in memory corruption. This can lead to arbitrary code execution or denial of service if a user opens a crafted PCX file with GIMP on a 32-bit system. The attack vector is local with high complexity and requires user interaction. Default security features such as SELinux, ASLR, and NX stack protection reduce the risk and impact of exploitation. There are no known exploits in the wild at this time.

No official patch or fix is currently confirmed. To mitigate this vulnerability, users should avoid opening PCX files from untrusted sources with GIMP, especially on 32-bit builds. Monitor the vendor advisory for updates on patches or official fixes.