# CVE-2026-53503

## Summary

- **CVE ID:** CVE-2026-53503
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-20, CWE-369
- **Published:** Jul 31, 2026
- **Last Modified:** Jul 31, 2026

## 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 Products

- thumbor — thumbor (< 7.8.0)

## References

- [CNA](https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9)
- [CNA](https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73)
- [CNA](https://github.com/thumbor/thumbor/releases/tag/7.8.0)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.41%
- **EPSS Percentile:** 34.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._