CVE-2026-53503

Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS

Published Jul 31, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-cqjp-jf4r-h5q9 Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
History
Type Values Removed Values Added
First Time appeared Thumbor
Thumbor thumbor
Vendors & Products Thumbor
Thumbor thumbor
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
Weaknesses CWE-20
CWE-369
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 31, 2026, 9:39 PM
Reserved
Jun 9, 2026, 5:05 PM
Status
Deferred
Published
Jul 31, 2026, 7:17 PM
Modified
Sep 8, 2026, 8:51 PM