CVE-2026-53503: Thumbor

High severity, CVSS 7.5. EPSS: 0.8% chance of exploitation in the next 30 days.

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: before 7.8.0 (fixed in 7.8.0)

Published 2026-07-31. Last modified 2026-09-08.