CVE-2026-53502 Thumbor has path traversal via post-validation URL decoding bypass in file_loader
Attacker can read arbitrary files outside the root directory via path traversal in Thumbor's file loader.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53502?
CVE-2026-53502 is a high-severity path traversal vulnerability in thumbor, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, file_loader decodes percent-encoded path segments after its root-boundary validation, allowing traversal outside FILE_LOADER_ROOT_PATH through watermark or frame filter input. This issue is fixed in 7.8.0.
Weakness: CWE-22
Which versions are affected by CVE-2026-53502?
3 open source packages ship an affected version, including thumbor.
| Package | Affected | Fixed in |
|---|---|---|
thumbor PyPI | All versions | 7.8.0 |
thumbor PyPI | All versions | 7.8.0 |
thumbor PyPI | All versions | 7.8.0 |
How do I fix CVE-2026-53502?
Upgrade thumbor to 7.8.0 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-53502 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53502 exists.
Sources
Also known as DEBIAN-CVE-2026-53502, GHSA-cj54-hpcc-gj6h, PYSEC-2026-3618, UBUNTU-CVE-2026-53502.