Vulnerability · Published Jul 31, 2026 · Assigned by GitHub_M
CVE-2026-53503Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
High 7.5
In plain English
A high-severity improper input validation in thumbor from thumbor. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(<matrix>, <columns>, <should_normalize>) filter passes the user-controlled <columns> value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns > 0. When columns=0, the C code triggers undefined behavior; on x86_64 this reliably results in a fatal divide-by-zero trap (SIGFPE) and crashes the Thumbor process, causing a remote denial of service. This issue is fixed in 7.8.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | thumbor | 7.8.0-1 | DEBIAN-CVE-2026-53503 |
| PyPI | thumbor | 7.8.0 | GHSA-cqjp-jf4r-h5q9 |
| PyPI | thumbor | 7.8.0 | PYSEC-2026-3619 |
| Ubuntu:26.04:LTS | thumbor | no fix listed | UBUNTU-CVE-2026-53503 |
Affected products (as reported)
Weakness: CWE-20, CWE-369 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9 x_refsource_CONFIRM
- https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73 x_refsource_MISC
- https://github.com/thumbor/thumbor/releases/tag/7.8.0 x_refsource_MISC