Vulnerability Description
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor’s HMAC validation can be bypassed due to the use of Python’s .replace() when removing the signature from the URL before validation. Since .replace() removes all occurrences of the substring, an attacker can insert the same signature multiple times in the URL and manipulate the final URL used for validation. This allows crafting URLs where the validated string differs from the actual requested resource, enabling loading images from unintended domains or paths. This issue is fixed in 7.8.0.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/thumbor/thumbor/commit/e3ae3e2500537b4d735df4144129a649374bb7
- https://github.com/thumbor/thumbor/releases/tag/7.8.0
- https://github.com/thumbor/thumbor/security/advisories/GHSA-mw3h-qjxj-6xg9
FAQ
What is CVE-2026-53501?
CVE-2026-53501 is a vulnerability with a CVSS score of 8.2 (HIGH). Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor’s HMAC validation can be bypassed due to the use of Python’s .replace() when removing the signature from the URL...
How severe is CVE-2026-53501?
CVE-2026-53501 has been rated HIGH with a CVSS base score of 8.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-53501?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.