VULNERABILITY INTELLIGENCE
CVE-2026-53501
CVSS score8.2 HIGH
EPSS probability0.35%
CISA KEVNot currently listed
Published2026-07-31
Last modified2026-09-08
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
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.
Weakness classification
- CWE-347: Improper Verification of Cryptographic Signature