CVE-2026-66757: 
Linux Debian vulnerability analysis and mitigation

CVE-2026-66757 is an integer overflow vulnerability in the file-sgi plugin of GIMP that causes a denial of service when processing crafted RLE-compressed SGI images. When both ysize and zsize header dimensions are set to their maximum 16-bit value (65535), their multiplication overflows a 32-bit signed integer before being passed to calloc, resulting in undefined behavior and plugin crash. The vulnerability affects all versions of GIMP as tracked by Red Hat. It was published on July 27, 2026, and carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat CVE, Red Hat Bugzilla).

The root cause is a signed integer overflow (CWE-190) in the file-sgi plugin's SGI image parser. The image header fields ysize and zsize are read as 16-bit unsigned integers; when both are set to 65535, the expression ysize * zsize is computed as a 32-bit signed integer multiplication, overflowing the 32-bit boundary (65535 × 65535 = 4,294,836,225, which exceeds INT_MAX). The resulting corrupted value is then passed to calloc for row table allocation, triggering undefined behavior that aborts the plugin. Exploitation requires a user to open a specially crafted SGI image file in GIMP, making user interaction a prerequisite (Red Hat Bugzilla, Red Hat CVE).

Successful exploitation results in a denial of service — specifically, the GIMP file-sgi plugin crashes when attempting to open the malicious image. There is no impact on confidentiality or integrity, as the overflow only affects memory allocation size calculation and causes an abort rather than memory corruption leading to code execution. The scope is limited to the GIMP process on the local system, with no potential for lateral movement or data exfiltration (Red Hat CVE, Red Hat Bugzilla).

1. Craft malicious SGI file: Create an RLE-compressed SGI image file with the ysize and zsize header fields both set to 65535 (0xFFFF), which are valid 16-bit unsigned integer values accepted by the parser.
2. Deliver the file: Distribute the crafted .sgi file to a target user via email attachment, file share, web download, or other social engineering means.
3. Trigger parsing: Convince the target user to open the crafted SGI file in GIMP (e.g., by disguising it or placing it in a directory the user browses).
4. Overflow triggered: The file-sgi plugin reads ysize and zsize, computes ysize * zsize as a 32-bit signed integer (overflowing to a small or negative value), and passes the corrupted size to calloc.
5. Denial of service achieved: The undefined behavior causes the plugin to abort, crashing the GIMP SGI file-loading operation (Red Hat Bugzilla).

• File System: Presence of unexpected .sgi image files with unusually small file sizes relative to their declared dimensions (65535×65535 pixels) in user download directories or temp folders.
• Logs: GIMP crash reports or core dumps referencing the file-sgi plugin; application error logs showing abrupt termination during SGI image loading.
• Process: GIMP process terminating unexpectedly shortly after opening an SGI file, potentially generating a crash report or signal (e.g., SIGABRT) traceable to the sgi-lib component.

No vendor patch has been released as of the disclosure date; the CVE status remains "Awaiting Analysis" with no fixed version listed. Users should exercise caution when opening SGI image files from untrusted sources in GIMP. As a workaround, administrators can restrict access to SGI file processing or disable the file-sgi plugin if it is not required. Monitor the Red Hat CVE page and GIMP upstream repository for patch availability (Red Hat CVE, GNOME GitLab).