CVE-2026-53500: Thumbor SSRF via unescaped dots in ALLOWED_SOURCES

CVE-2026-53500 · Severity: high · CVSS 8.2 · Published 2026-07-31

Thumbor, an open-source photo thumbnail service, contains a security flaw in how it validates image sources. The service is designed to only fetch images from trusted websites, but a configuration error allows attackers to bypass these restrictions by using hostnames that look similar to trusted ones. This could allow an attacker to use the service to access internal data or unauthorized external content, potentially leading to data exposure or service misuse.

Technologies: thumbor (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-53500 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-53500 being exploited in the wild.
How severe is CVE-2026-53500?
High severity, with a CVSS score of 8.2, 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-2026-53500?
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-2026-53500 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-53500?
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 Server-Side Request Forgery (SSRF) vulnerability exists in Thumbor's HTTP loader due to improper sanitization of the ALLOWED_SOURCES configuration. When hostnames are provided as plain strings in the configuration, they are passed directly to Python's re.match() without escaping. Because the dot character (.) is a regex wildcard, an attacker can bypass the allowlist by using a domain that matches the pattern but replaces dots with other characters (e.g., 'sXglbimgYcom' matching 's.glbimg.com'). This allows for unauthorized image fetching from arbitrary hosts. The issue is resolved in version 7.8.0 by applying re.escape() to string-based patterns.

Affected products

  • globo.com thumbor < 7.8.0

Identifiers

  • CVE-2026-53500
  • GHSA-6x26-6r6f-m537
  • PYSEC-2026-3617

Timeline

  • 2026-05-30: patched: Fix committed to repository and version 7.8.0 released.
  • 2026-06-10: advisory: GitHub Security Advisory GHSA-6x26-6r6f-m537 published.
  • 2026-07-31: disclosed: CVE-2026-53500 published to NVD.

References

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