Pillow: TiffDecode returns uninitialized memory as pixels for short JPEG strips

Pillow is a Python imaging library. From 5.3.0 until 13.0.0, Pillow can return uninitialized memory as pixels when libtiff performs a short decode of JPEG-compressed or Group 4 fax TIFF data. The _decodeStrip and _decodeTile buffers can be larger than the bytes written by libtiff, but Pillow converts the expected rows without clearing the unwritten tail. The tile path is affected from 5.3.0 and the strip path from 6.0.0. An attacker can supply a crafted TIFF to an application that loads and returns or re-encodes its pixels. This can disclose stale heap contents without memory corruption or a process crash. This issue is fixed in version 13.0.0.

Source published

19 Oct 2026 22:00:52 UTC

Source modified

22 Oct 2026 21:13:16 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N