CVE-2026-53504: Thumbor ReDoS in convolution filter

CVE-2026-53504 · Severity: high · CVSS 7.5 · Published 2026-07-31

Thumbor is an open-source service used to resize and process images on the fly. A flaw in how it handles certain image filters allows an attacker to send a specially crafted web request that freezes the service. This can lead to a total service outage, preventing legitimate users from viewing or processing images.

Technologies: thumbor (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-53504 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-53504 being exploited in the wild.
How severe is CVE-2026-53504?
High severity, with a CVSS score of 7.5, published 31 July 2026.
Which products and versions are affected?
thumbor (PyPI) <= 7.7.7, ECOSYSTEM:introduced=0,fixed=7.8.0.
Is there a fix for CVE-2026-53504?
Yes. thumbor (PyPI): upgrade to 7.8.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-53504 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-53504?
Check whether you run thumbor (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • thumbor (PyPI): upgrade to 7.8.0 or later
    pip install "thumbor>=7.8.0"

Technical details

A Regular Expression Denial of Service (ReDoS) vulnerability exists in the convolution filter of Thumbor. The root cause is an inefficient regular expression used to parse filter parameters, specifically a subpattern that behaves like (\d+)*,\d+, which triggers exponential backtracking when processing long strings of repeated numeric input. An unauthenticated remote attacker can exploit this by sending a crafted URL containing a malformed convolution filter string. This causes the Python interpreter to exhaust CPU resources while attempting to match the expression, leading to a denial of service for the image processing worker. The issue is resolved in version 7.8.0 by replacing the ambiguous regex with a non-backtracking alternative.

Affected products

  • thumbor thumbor < 7.8.0

Identifiers

  • CVE-2026-53504
  • GHSA-5vjc-7cxw-4w6j
  • PYSEC-2026-3616

Timeline

  • 2026-05-30: patched: Version 7.8.0 released
  • 2026-06-10: advisory: GitHub Security Advisory published
  • 2026-07-31: disclosed: CVE published to NVD

References

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