# 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.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-53502, GHSA-cj54-hpcc-gj6h, PYSEC-2026-3618, UBUNTU-CVE-2026-53502

## 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 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-53502?

3 open source packages ship an affected version, including thumbor.


| Package | Ecosystem | 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.

## Is CVE-2026-53502 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53502 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53502 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53502 exists.

Affected packages and fixed versions:
- thumbor (PyPI): affected all versions; fixed in 7.8.0
- thumbor (PyPI): affected all versions; fixed in 7.8.0
- thumbor (PyPI): affected all versions; fixed in 7.8.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53502/ (Markdown: https://insights.sbomify.com/CVE-2026-53502/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53502
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53502
- OSV: https://osv.dev/vulnerability/CVE-2026-53502

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53502/
Summaries are generated and may contain mistakes; the official description above is the record.