Pillow EUVD-2026-104641

Exploitation requires the application to invoke Image.transform() using the fast path - specifically Transform.EXTENT or a pure scale-and-translate Transform.AFFINE with the default NEAREST resampling filter - on an operation large enough that memory allocation is strained. The precise trigger is a selective allocation failure: the output image allocation must succeed while the additional per-column lookup allocation fails, so the host must be under genuine memory pressure for the vulnerable error path to execute. Limiting factors: the attacker must be able to influence transform size/parameters (typically via an image-upload or image-processing feature), reliable triggering depends on the non-deterministic memory-pressure window rather than a guaranteed condition, and only Pillow versions prior to 13.0.0 are affected. There is no authentication requirement in the supplied CVSS vector (PR:N) and no user interaction (UI:N).

The input CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) scores 8.7 (High) and is driven entirely by availability impact (VA:H) with no confidentiality or integrity impact - this is fundamentally a denial-of-service/memory-corruption bug, not a disclosure or code-execution flaw as confirmed. No EPSS score, KEV listing, or POC was provided, so the signal set is thin: no public exploit identified at time of analysis and no evidence of active exploitation. The AC:L/AT:N rating in the supplied vector conflicts with the description, which requires the attacker to 'drive such a large Image.transform() operation under memory pressure' such that the output allocation succeeds while the per-column lookup allocation selectively fails - this is a probabilistic, environment-dependent precondition, not a deterministic low-complexity trigger, so the real-world reliability is considerably lower than 8.7 implies. The description also hedges impact as 'may trigger', 'can crash', and 'may corrupt memory', meaning the worst-case (exploitable memory corruption → code execution) is unconfirmed and speculative; the confirmed outcome is a process crash. Net assessment: a genuine bug worth patching in exposed image-processing pipelines, but closer to a conditional DoS than a widely-weaponizable critical issue, and the raw high CVSS overstates priority absent exploit evidence.

A web service that accepts user-supplied images and performs resize/transform operations (e.g. thumbnailing via Image.transform with EXTENT or scale-and-translate AFFINE under default NEAREST resampling) is targeted by an attacker who submits a very large transform request while the host is under memory pressure. If the output image allocation succeeds but the subsequent per-column lookup allocation fails, the error path double-frees image storage, crashing the worker process and potentially corrupting memory. No public exploit code is identified, and reliable triggering depends on inducing the specific allocation-failure window.