CVE-2026-53501 (GCVE-0-2026-53501)
Vulnerability from cvelistv5 – Published: 2026-07-31 18:42 – Updated: 2026-07-31 19:58
VLAI
EPSS
VEX
Title
Thumbor has HMAC validation bypass via multiple .replace() calls when removing URL signature
Summary
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.
Severity
8.2 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-31 19:57 UTC
CWE
- CWE-347 - Improper Verification of Cryptographic Signature
Assigner
GitHub_M
CNA
References
3 references
| URL | Tags |
|---|---|
| https://github.com/thumbor/thumbor/security/advis… | x_refsource_CONFIRM |
| https://github.com/thumbor/thumbor/commit/e3ae3e2… | x_refsource_MISC |
| https://github.com/thumbor/thumbor/releases/tag/7.8.0 | x_refsource_MISC |
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