CVE-2026-27809
CVE-2026-27809 is a CWE-190 vulnerability in psd-tools. O3 Security confirms whether CVE-2026-27809 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
psd-tools: Compression module has unguarded zlib decompression, missing dimension validation, and hardening gaps
Blast Radius
psd-toolsReal-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
psd-tools is a Python package for working with Adobe Photoshop PSD files. Prior to version 1.12.2, when a PSD file contains malformed RLE-compressed image data (e.g. a literal run that extends past the expected row size), decode_rle() raises ValueError which propagated all the way to the user, crashing psd.composite() and psd-tools export. decompress() already had a fallback that replaces failed channels with black pixels when result is None, but it never triggered because the ValueError from decode_rle() was not caught. The fix in version 1.12.2 wraps the decode_rle() call in a try/except so the existing fallback handles the error gracefully.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | psd-tools | all versions | 1.12.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for psd-tools. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update psd-tools to 1.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27809 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-27809 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-27809. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-27809 in your dependencies?
O3 detects CVE-2026-27809 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.