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Vulnerability record · CVE-2026-53503 · published 31 July 2026

CVE-2026-53503: Improper input validation vulnerability

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.

7.5 CVSS 3.1 High EPSS 0.75% · top 46.9% CWE-20 · Improper input validationCWE-369 · Divide by zero Deferred
7.5CVSS 3.1 base score
0.75%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
8 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

LinkTags
https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73
https://github.com/thumbor/thumbor/releases/tag/7.8.0
https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9
https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9

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Source: NIST National Vulnerability Database (record CVE-2026-53503), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.