CVE-2026-59204 — pillow
Fix: python-pillow/Pillow@13ada41CVE-2026-59204 is a CWE-789 vulnerability in pillow. A fix is available for pillow — see the affected versions and patch details below.
Pillow JPEG2000 tiled decode retains a growing scratch buffer and can be used for denial of service
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59204.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
pillowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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 1832
Expected 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.jp2
Load it again under a 160 MB address-space cap:
python exercise_j2k_tile_realloc.py load poc_3664_rgba_tile1832.jp2 --limit-mb 160
Impact
Conservative impact: denial of service through memory exhaustion during JPEG2000 decoding.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pillow | ≥ 8.2.0&&< 12.3.0 | 12.3.0pip install --upgrade 'pillow==12.3.0' |
Affected Products
pillowpythonDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pillow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pillow to 12.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59204 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
The impact is limited to denial of service via excessive memory allocation. A crafted JPEG2000 file can trigger out-of-memory failures, but this does not lead to code execution or information disclosure.
If the application does not need JPEG2000 support, block .jp2, .j2k, .jpf, and .jpx uploads at the input layer. For services that do process JPEG2000, set memory limits on the process or container (LimitAS= in systemd, or memory limits in Kubernetes/Podman) so a crafted image can only crash the worker, not the whole host. Add automatic restarts (Restart=always in systemd, or container restart policies) so the service recovers from OOM kills without someone having to intervene.Source: Red Hat security advisory for CVE-2026-59204 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat AI Inference Server 3.2 | rhaiis/vllm-cuda-rhel9:1787860580 | RHSA-2026:61627 |
| Red Hat AI Inference Server 3.2 | rhaiis/model-opt-cuda-rhel9:1787772157 | RHSA-2026:61628 |
| Red Hat AI Inference Server 3.2 | rhaiis/vllm-rocm-rhel9:1787884873 | RHSA-2026:61629 |
| Red Hat AI Inference Server 3.3 | rhaiis/model-opt-cuda-rhel9:1787601159 | RHSA-2026:59518 |
| Red Hat AI Inference Server 3.4 | rhaii/vllm-spyre-rhel9:1789681201 | RHSA-2026:69464 |
| Red Hat AI Inference Server 3.4 | rhaii/vllm-cpu-rhel9:1789681128 | RHSA-2026:69466 |
| Red Hat AI Inference Server 3.4 | rhaii/vllm-cuda-rhel9:1789681126 | RHSA-2026:69467 |
| Red Hat AI Inference Server 3.4 | rhaii/model-opt-cuda-rhel9:1789681126 | RHSA-2026:69468 |
Frequently Asked Questions
Is CVE-2026-59204 in your dependencies?
Find it across PyPI, including transitive dependencies.