Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter (CVE-2026-53504)
### 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 new images won't be processed until `re.match` returns.
Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter (CVE-2026-53504)
Description
### 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 new images won't be processed until `re.match` returns.
CVSS v3.1
Score 7.5high
Affected software
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Weaknesses
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-5vjc-7cxw-4w6j
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-53504"]
- Ecosystems
- ["PyPI"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a6d13b0bf32cb7a34580132
Added to database: 07/31/2026, 21:29:20 UTC
Last updated: 07/31/2026, 21:29:20 UTC
Views: 1
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