Pillow EUVD-2026-104636

Exploitation requires a specific application coding pattern, not just a vulnerable Pillow version: the consuming application must catch Image.DecompressionBombError and then continue to call seek() or load() on the SAME GifImageFile object that raised it. Only then are the rejected, oversized frame dimensions (retained in GifImagePlugin._seek before the fix) used for a subsequent allocation. The required input is a crafted multi-frame GIF whose declared frame extents exceed Pillow's decompression-bomb limit. Limiting factors: the attack is purely a denial of service (no code execution, data disclosure, or integrity impact); applications that let the exception propagate, discard the image object on error, or do not process further frames are NOT affected; it affects only GIF handling; and it is fixed in 13.0.0.

This is a CWE-400 uncontrolled-resource-consumption (memory exhaustion) denial-of-service flaw in Pillow, an extremely widely used Python imaging library (9.2.0 through pre-13.0.0). The input CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) with VA:H scores 8.7 (High), reflecting a network-reachable, unauthenticated, availability-only impact with no confidentiality or integrity effect. However, the raw score overstates real-world risk because exploitation is NOT automatic against default usage: the description makes clear it only triggers when an application catches the Image.DecompressionBombError and then continues to seek/load the SAME image object - a non-default, defensive-but-flawed error-handling pattern. The provided AT:N (no attack requirements) therefore understates reality; a conditional precondition exists, so AT:P is more honest. No EPSS score, KEV listing, or POC was supplied: exploitation status is 'no public exploit identified at time of analysis,' and there is no evidence of active exploitation. Net: a legitimate but bounded DoS - worth patching promptly in services that process untrusted GIFs, but not a widespread drive-by threat, and the absence of EPSS/KEV signals argues against urgent emergency response.

An attacker uploads or submits a crafted GIF to a Python web service that uses Pillow and has wrapped image decoding in a try/except that catches DecompressionBombError and then continues to seek or load further frames of the same Image object. The retained oversized frame dimensions cause a large allocation on the next seek/load, exhausting memory and crashing or hanging the worker. No public exploit code was provided in the input, and the attack requires network access only (AV:N) with low complexity once the vulnerable error-handling pattern is present.