OpenImageIO CVE-2026-63422

Exploitation requires the victim to read/process a crafted tiled OpenEXR image whose width is NOT an exact multiple of its tile width, and specifically to read a partial edge-tile rectangle via OpenEXRInput::read_native_tiles() (both the classic and OpenEXR-Core readers in src/openexr.imageio/exrinput.cpp are affected). The trigger is that source rows are spaced by the padded whole-tile scanline_stride while the caller's buffer is sized to the requested rectangle width, so the copy overruns. Limiting factors: local attack vector (AV:L) with required user interaction (UI:R) - an operator or automated pipeline must actually open/decode the malicious file; no authentication is needed (PR:N). Not exploitable against builds already at 3.0.21.0, 3.1.16.0, or 3.2.0.3-beta1.

This is a genuine memory-corruption bug (CWE-122 heap out-of-bounds write) rather than a high-CVSS-but-low-real-risk issue, but its exploitability is bounded by the CVSS attack vector. The vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H is local with required user interaction - the attacker cannot reach the code remotely on their own; a victim must open or process a crafted tiled OpenEXR file. The 7.8 base score is driven by the C:H/I:H/A:H impact triad typical of an out-of-bounds write, which is consistent with the described heap corruption. No EPSS score, no CISA KEV listing, and no weaponized public exploit are present in the provided data, so this is not confirmed as actively exploited; the signals point to a serious-but-not-yet-exploited memory-safety flaw. One caveat: while there is no packaged exploit, the fixing PR (#5295) ships a full regression test that deterministically generates a triggering image (a 127x129 tiled EXR with 64x64 tiles) and drives read_native_tiles(), so the trigger conditions and a reproducer are effectively public - lowering the effort to build a PoC even though none is cataloged as such.

An attacker crafts a tiled OpenEXR image whose width is not a multiple of the tile width and delivers it to a victim (e.g., via an asset pack, render job, or shared VFX file). When the victim's OpenImageIO-based application reads a partial edge-tile rectangle, read_native_tiles() copies rows using the padded whole-tile stride, producing a heap out-of-bounds write and memory corruption. No packaged exploit is cataloged, but the upstream fix includes a regression test that generates a triggering image, so a reproducer is effectively public.