PYSEC-2026-3616
Vulnerability from pysec - Published: 2026-08-04 11:34 - Updated: 2026-08-04 13:36Summary
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.
| Name | purl | thumbor | pkg:pypi/thumbor |
|---|
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "thumbor",
"purl": "pkg:pypi/thumbor"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "7.8.0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"4.1.3",
"4.10.0",
"4.10.1",
"4.10.2",
"4.10.3",
"4.11.0",
"4.11.1",
"4.12.0",
"4.12.1",
"4.12.2",
"4.4.1",
"4.5.3",
"4.5.4",
"4.6.0",
"4.7.0",
"4.7.1",
"4.8.0",
"4.8.1",
"4.8.2",
"4.8.3",
"4.8.4",
"4.8.5",
"4.8.6",
"4.9.0",
"4.9.1",
"5.0.0",
"5.0.0rc1",
"5.0.0rc2",
"5.0.1",
"5.0.2",
"5.0.3",
"5.0.4",
"5.0.5",
"5.0.6",
"5.1.0",
"5.2.0",
"5.2.1",
"6.0.0",
"6.0.0b1",
"6.0.0b2",
"6.0.0b3",
"6.0.0b4",
"6.0.0b5",
"6.0.1",
"6.0.2",
"6.1.0",
"6.1.1",
"6.1.2",
"6.1.3",
"6.1.4",
"6.1.5",
"6.2.0",
"6.2.1",
"6.3.0",
"6.3.1",
"6.3.2",
"6.4.0",
"6.4.1",
"6.4.2",
"6.4.3",
"6.5.0",
"6.5.1",
"6.5.2",
"6.6.0",
"6.6.1",
"6.7.0",
"6.7.1",
"6.7.2",
"6.7.3",
"6.7.4",
"6.7.5",
"6.7.6",
"7.0.0",
"7.0.0a1",
"7.0.0a2",
"7.0.0a3",
"7.0.0a4",
"7.0.0a5",
"7.0.0b1",
"7.0.1",
"7.0.10",
"7.0.11",
"7.0.12",
"7.0.2",
"7.0.3",
"7.0.5",
"7.0.6",
"7.0.7",
"7.0.8",
"7.0.9",
"7.1.0",
"7.1.1",
"7.1.2",
"7.2.0",
"7.2.1",
"7.3.0",
"7.3.1",
"7.3.2",
"7.4.0",
"7.4.1",
"7.4.2",
"7.4.3",
"7.4.4",
"7.4.5",
"7.4.6",
"7.4.7",
"7.5.0",
"7.5.1",
"7.5.2",
"7.6.0",
"7.7.0",
"7.7.1",
"7.7.2",
"7.7.3",
"7.7.4",
"7.7.5",
"7.7.6",
"7.7.7"
]
}
],
"aliases": [
"CVE-2026-53504",
"GHSA-5vjc-7cxw-4w6j"
],
"details": "### Summary\nThe regular expression used to parse the `convolution` filter exhibits exponential-time backtracking for certain inputs, enabling a Regular Expression Denial of Service (ReDoS).\n\n### Details\nThe 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+`.\n\n### PoC\nA filter string containing many repeated values will exhaust `re.match`:\n- `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)`\n- 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\n\nThe evaluation occurs on https://github.com/thumbor/thumbor/blob/master/thumbor/filters/__init__.py#L189.\n\n### Impact\nA specially crafted URL will lead to denial of service, as new images won\u0027t be processed until `re.match` returns.",
"id": "PYSEC-2026-3616",
"modified": "2026-08-04T13:36:37.885545Z",
"published": "2026-08-04T11:34:46.398484Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/thumbor/thumbor/security/advisories/GHSA-5vjc-7cxw-4w6j"
},
{
"type": "WEB",
"url": "https://github.com/thumbor/thumbor/commit/3f38fe1610d20168e91f76d432212de30727eb2e"
},
{
"type": "PACKAGE",
"url": "https://github.com/thumbor/thumbor"
},
{
"type": "WEB",
"url": "https://github.com/thumbor/thumbor/releases/tag/7.8.0"
},
{
"type": "PACKAGE",
"url": "https://pypi.org/project/thumbor"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-5vjc-7cxw-4w6j"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53504"
}
],
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.