PT-2026-66842 · Thumbor · Thumbor

CVE-2026-53505 · Published 2026-07-31 · Updated 2026-07-31

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions Thumbor versions prior to 7.8.0

Description The filters:proportion(<value>) filter does not enforce an upper bound on the value parameter and operates during the post-transform phase. This allows an attacker to trigger extremely large image resizes, leading to CPU and memory exhaustion, which results in a denial of service. Because the filter runs after the main transform pipeline, it can bypass request-level size clamping mechanisms such as MAX WIDTH and MAX HEIGHT. The issue is located in the thumbor/filters/proportion.py file, where the value is parsed as a float without a maximum limit, subsequently calculating new width and new height before calling the engine.resize() function.

Recommendations Update to version 7.8.0. As a temporary workaround, restrict access to the filters:proportion() filter or disable the /unsafe/ URL option to minimize the risk of unauthenticated exploitation.

Fix

Resource Exhaustion

Weakness Enumeration

CWE-400

Related Identifiers

CVE-2026-53505

GHSA-PHJ3-59PF-CP83

Affected Products

Thumbor

References · 6

• https://osv.dev/vulnerability/GHSA-phj3-59pf-cp83 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-53505 · Security Note
• https://github.com/thumbor/thumbor/commit/2c716119de986cfc68c7071af52a98187e006023 · Note
• https://github.com/thumbor/thumbor/security/advisories/GHSA-phj3-59pf-cp83 · Note
• https://github.com/thumbor/thumbor/releases/tag/7.8.0 · Note
• https://github.com/thumbor/thumbor · Note