Pillow JPEG2000 tiled decode retains a growing scratch buffer and can be used for denial of service
Summary
src/libImaging/Jpeg2KDecode.c:853 accumulates total_component_width across every tile in a JPEG2000 image instead of recomputing it per tile. That accumulated value is then used in the tile_bytes calculation at src/libImaging/Jpeg2KDecode.c:868, which can make the decoder grow state->buffer via realloc at src/libImaging/Jpeg2KDecode.c:876 up to roughly one full image's decompressed size even when each tile is small. A crafted tiled JPEG2000 file can therefore force substantially higher transient memory usage and trigger out-of-memory failures during decoding. Based on current evidence, the supported impact is denial of service, not memory corruption.
Details
- Location:
src/libImaging/Jpeg2KDecode.c:853 - Root cause:
total_component_widthis initialized only once before the tile loop and keeps growing across tiles. It is then used to derivetile_bytes, so later tiles are treated as if they had the combined component width of all earlier tiles. - Dangerous operation:
tile_bytesis promoted intotile_info.data_size, thenstate->bufferis grown withreallocatsrc/libImaging/Jpeg2KDecode.c:876. - Reachability: any attacker-controlled JPEG2000 image with many tiles reaches this path during normal
Image.open(...).load()decoding.
PoC
The attached helper script and testcase were used: exercise_j2k_tile_realloc.zip
Generate the testcase:
pythonexercise_j2k_tile_realloc.py make poc_3664_rgba_tile1832.jp2 \
--size 3664 --tile 1832Expected geometry from the helper:
- image size:
3664 x 3664 - mode:
RGBA - tile size:
1832 x 1832(2x2tiles) image_bytes=53699584- uncapped RSS observed:
- vulnerable build:
maxrss_kb=180264 - fixed comparison build:
maxrss_kb=138404
- vulnerable build:
Load it with the current vulnerable build:
python exercise_j2k_tile_realloc.py load poc_3664_rgba_tile1832.jp2Load it again under a 160 MB address-space cap:
python exercise_j2k_tile_realloc.py load poc_3664_rgba_tile1832.jp2 --limit-mb 160Impact
Conservative impact: denial of service through memory exhaustion during JPEG2000 decoding.
Czego dotyczy
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| Platforma | Paczka | Podatne wersje | Poprawka w wersji |
|---|---|---|---|
| Python (PyPI) | pillow | >= 8.2.0, < 12.3.0 | 12.3.0 |
Odnośniki
- https://github.com/python-pillow/Pillow/security/advisories/GHSA-vjc4-5qp5-m44j
- https://nvd.nist.gov/vuln/detail/CVE-2026-59204
- https://github.com/python-pillow/Pillow/pull/9704
- https://github.com/python-pillow/Pillow/commit/13ada41172142f2fd9f0906f615a00ea623a11ca
- https://github.com/python-pillow/Pillow
- https://github.com/python-pillow/Pillow/releases/tag/12.3.0
- https://pypi.org/project/pillow
- https://github.com/advisories/GHSA-vjc4-5qp5-m44j
- Wektor CVSS
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N- Słabość (CWE)
CWE-770, CWE-789- Platforma
- Python (PyPI)
- Paczka
pillow- Ujawniono
- 20.07.2026
- Aktualizacja
- 11.10.2026 15:17
Źródła i licencje
OSV / GitHub Advisory Database - PYSEC-2026-3496 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-vjc4-5qp5-m44j - CC BY 4.0
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