Thumbor has Regex Denial of Service (ReDoS) in convolution filter

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-53504: 0.61% estimated exploitation activity in the next 30 days; percentile 49.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The regular expression used to parse the convolution filter exhibits exponential-time backtracking for certain inputs, enabling a Regular Expression Denial of Service (ReDoS). Details The RegExp for convolution is defined as convolution\((?:\s((?:[-]?[\d]+\.?[\d][;])(?:[-]?[\d]+\.?[\d]))\s)(?:,\s([\d]+)\s)(?:,\s([Tt]rue|[Ff]alse|1|0)\s)?\). Within this expression a dangerous subpattern effectively behaves like (\d+),\d+. PoC A filter string containing many repeated values will exhaust re.match: - convolution(-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11) - http://localhost:8888/unsafe/0x0/smart/filters:convolution(-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11)/x.png The evaluation occurs on https://github.com/thumbor/thumbor/blob/master/thumbor/filters/init.py#L189. Impact A specially crafted URL will lead to denial of service, as…

Published by the source

31 Jul 2026, 18:58 UTC

Last modified by the source

31 Jul 2026, 18:58 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5vjc-7cxw-4w6j

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# Patch Next advisory brief: CVE-2026-53504

Advisory: Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter
IDs: CVE-2026-53504, GHSA-5vjc-7cxw-4w6j
Record: https://patchnext.com/advisories/cve-2026-53504 (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: thumbor 7.8.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI thumbor: affected <= 7.7.7; fixed in 7.8.0

## Suggested inspection (read-only)
- `python -m pip show thumbor`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on thumbor.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5vjc-7cxw-4w6j (GitHub-reviewed advisory GHSA-5vjc-7cxw-4w6j lists affected ranges: PyPI thumbor >=0 <=7.7.7)

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