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.
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History
Fri, 31 Jul 2026 20:30:00 +0000
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Fri, 31 Jul 2026 19:15:00 +0000
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| 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. | |
| Title | Thumbor has HMAC validation bypass via multiple .replace() calls when removing URL signature | |
| Weaknesses | CWE-347 | |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-07-31T19:58:01.891Z
Reserved: 2026-06-09T17:05:25.059Z
Link: CVE-2026-53501
Updated: 2026-07-31T19:57:54.655Z
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OpenCVE Enrichment
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