Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Thumbor versions before 7.8.0 are vulnerable to an HMAC validation bypass. The signature is removed from the request URL with a replace call that strips every occurrence, so an attacker who can send requests can insert extra copies of the signature to change the string being validated. This can let them load images from unintended domains or paths, effectively using the deployment as an open proxy. Upgrade to Thumbor 7.8.0 or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 8.2 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0035, the 29th percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:41 UTC First seen by agentprime
- 31 Oct 2026, 14:41 UTC Confirmed by OSV