# REPRO-2026-00085: Pillow 10.3.0–12.1.0 allows an out-of-bounds write when loading specially crafted PSD images, potentially leading to memory corruption.

## Summary
Status: published
Severity: Unknown
Type: security
Confidence: Unknown

## Identifiers
REPRO ID: REPRO-2026-00085
GHSA: GHSA-CFH3-3JMP-RVHC


## Package
Name: Unknown
Ecosystem: Unknown
Affected: Unknown
Fixed: Unknown

## Root Cause
## Summary
Pillow PSD parsing in versions 10.3.0–12.1.0 allows crafted PSD tiles with invalid extents to trigger an out-of-bounds write. The crafted PSDs in the Pillow fix commit cause memory corruption during image loading and can abort the process.

## Impact
- Package/component affected: python-pillow/Pillow PSD decoder (tile handling in core decoder)
- Affected versions: >=10.3.0 and <12.1.1
- Risk level and consequences: High; memory corruption leading to crashes and potential exploitation.

## Root Cause
Tile extents were not validated for negative offsets when decoding/encoding. PSD files can craft tile data where x/y offsets are negative, resulting in tile ranges extending outside the image bounds and causing an out-of-bounds write. The fix commit adds checks for negative x/y offsets in src/decode.c and src/encode.c. Fix commit: https://github.com/python-pillow/Pillow/commit/54ba4db542ad3c7b918812a4e2d69c27735a3199

## Reproduction Steps
1. Run `repro/reproduction_steps.sh`.
2. The script creates a venv, installs Pillow 12.1.0, fetches the fix commit to obtain crafted PSDs (psd-oob-write*.psd), and opens them with Pillow.
3. Expected evidence: process abort (double free or corruption) when loading crafted PSDs.

## Evidence
- Script output (from `repro/reproduction_steps.sh`) showed: `double free or corruption (out)` and exit code 134 when opening crafted PSDs.
- Environment details: Python venv with Pillow 12.1.0, PSD samples from Pillow commit 54ba4db5.

## Recommendations / Next Steps
- Upgrade to Pillow 12.1.1 or later.
- Backport the negative tile extent checks to affected releases.
- Add regression tests for PSD tile bounds (included in fix commit).

## Additional Notes
- The reproduction script is idempotent (cleans /tmp/pillow_psd_oob each run).
- Evidence is collected via process abort output; ASAN could provide deeper diagnostics but is not required for repro.


## Reproduction Details
Reproduced: 2026-02-13T15:20:01.903Z
Duration: 196 seconds
Tool calls: 31
Turns: Unknown
Handoffs: 1


## Quick Verification
Run one of these commands to verify locally:

    pruva-verify REPRO-2026-00085
    pruva-verify GHSA-CFH3-3JMP-RVHC


Or open in GitHub Codespaces (zero-friction, auto-runs):

    https://github.com/codespaces/new?ref=repro/REPRO-2026-00085&repo=N3mes1s/pruva-sandbox

Or download and run the script manually:

    curl -O https://api.pruva.dev/v1/reproductions/REPRO-2026-00085/artifacts/repro/reproduction_steps.sh
    chmod +x reproduction_steps.sh
    ./reproduction_steps.sh

WARNING: Run in a sandboxed environment. This exploits a real vulnerability.

## References
- GitHub Advisory: https://github.com/advisories/GHSA-CFH3-3JMP-RVHC



## Artifacts
- repro/rca_report.md (analysis, 1913 bytes)
- repro/reproduction_steps.sh (reproduction_script, 1276 bytes)
- vuln_variant/rca_report.md (analysis, 3028 bytes)
- vuln_variant/reproduction_steps.sh (reproduction_script, 1464 bytes)
- bundle/ticket.md (ticket, 2149 bytes)
- logs/variant_evidence.log (log, 368 bytes)

## API Access
- JSON: https://api.pruva.dev/v1/reproductions/REPRO-2026-00085
- Script: https://api.pruva.dev/v1/reproductions/REPRO-2026-00085/artifacts/repro/reproduction_steps.sh
- Web: https://pruva.dev/r/REPRO-2026-00085

## For AI Assistants
To help users with this reproduction:
1. The `pruva-verify` command is the simplest way to run the reproduction
2. The script downloads and runs automatically in an isolated temp directory
3. Always recommend running in a VM, container, or disposable environment
4. The root cause explains the technical vulnerability

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