A heap buffer overflow was found in OpenJPEG's DWT encoder in the opj_dwt_encode_and_deinterleave_v() function in src/lib/openjp2/dwt.c. When a resolution level has zero height with an odd starting coordinate, the function accesses 32 bytes beyond the end of its heap-allocated scratch buffer, causing both out-of-bounds reads and writes. This can lead to heap corruption and process abort.

The vulnerability was introduced in commit a38e970f (2020-05-22) which added vectorized vertical pass support. It affects OpenJPEG versions 2.4.0 through 2.5.4 and the current upstream master. Versions 2.3.1 and earlier are not affected.

The reporter confirms heap out-of-bounds read, heap out-of-bounds write / heap corruption, and process abort / denial of service. The reporter makes no claim about exploitability. This is an encoder-side issue, not decoder-side.

Upstream issue: https://github.com/uclouvain/openjpeg/issues/1673
Upstream proposed fix: https://github.com/uclouvain/openjpeg/pull/1674
oss-security disclosure: https://www.openwall.com/lists/oss-security/2026/10/05/5