Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter
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
/x.png){kind=link}
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 new images won't be processed until re.match returns.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | thumbor | < 7.8.0 | 7.8.0 |
References
- https://github.com/thumbor/thumbor/security/advisories/GHSA-5vjc-7cxw-4w6j
- https://github.com/thumbor/thumbor/commit/3f38fe1610d20168e91f76d432212de30727eb2e
- https://github.com/thumbor/thumbor
- https://github.com/thumbor/thumbor/releases/tag/7.8.0
- https://pypi.org/project/thumbor
- https://github.com/advisories/GHSA-5vjc-7cxw-4w6j
- https://nvd.nist.gov/vuln/detail/CVE-2026-53504
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
thumbor- Disclosed
- 31.07.2026
- Updated
- 11.10.2026 14:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-3616 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5vjc-7cxw-4w6j - CC BY 4.0
Vulnerability history: thumbor
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 6
- First → latest
- 07.2026 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 6
Disclosures per year
- 2026: 6
-
Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter this entry
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