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[GHSA-9wv6-86v2-598j] path-to-regexp outputs backtracking regular expressions #4795

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Sep 12, 2024
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[GHSA-9wv6-86v2-598j] path-to-regexp outputs backtracking regular expressions #4795

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35 changes: 25 additions & 10 deletions advisories/github-reviewed/2024/09/GHSA-9wv6-86v2-598j/GHSA-9wv6-86v2-598j.json
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{
"schema_version": "1.4.0",
"id": "GHSA-9wv6-86v2-598j",
"modified": "2024-09-11T17:17:47Z",
"modified": "2024-09-11T17:17:48Z",
"published": "2024-09-09T20:19:15Z",
"aliases": [
"CVE-2024-45296"
],
"summary": "path-to-regexp outputs backtracking regular expressions",
"details": "### Impact\n\nA bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (`.`). For example, `/:a-:b`.\n\n### Patches\n\nFor users of 0.1, upgrade to `0.1.10`. All other users should upgrade to `8.0.0`.\n\nThese versions add backtrack protection when a custom regex pattern is not provided:\n\n- [0.1.10](https://github.com/pillarjs/path-to-regexp/releases/tag/v0.1.10)\n- [1.9.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v1.9.0)\n- [3.3.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v3.3.0)\n\nThey do not protect against vulnerable user supplied capture groups. Protecting against explicit user patterns is out of scope for this library and not considered a vulnerability.\n\nVersion [7.1.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v7.1.0) can enable `strict: true` and get an error when the regular expression might be bad.\n\nVersion [8.0.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v8.0.0) removes the features that can cause a ReDoS.\n\n### Workarounds\n\nAll versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change `/:a-:b` to `/:a-:b([^-/]+)`.\n\nIf paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. For example, halving the attack string improves performance by 4x faster.\n\n### Details\n\nUsing `/:a-:b` will produce the regular expression `/^\\/([^\\/]+?)-([^\\/]+?)\\/?$/`. This can be exploited by a path such as `/a${'-a'.repeat(8_000)}/a`. [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS) has a good example of why this occurs, but the TL;DR is the `/a` at the end ensures this route would never match but due to naive backtracking it will still attempt every combination of the `:a-:b` on the repeated 8,000 `-a`.\n\nBecause JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and can lead to a DoS. In local benchmarks, exploiting the unsafe regex will result in performance that is over 1000x worse than the safe regex. In a more realistic environment using Express v4 and 10 concurrent connections, this translated to average latency of ~600ms vs 1ms.\n\n### References\n\n* [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS)\n* [Detailed blog post](https://blakeembrey.com/posts/2024-09-web-redos/)",
"details": "### Impact\n\nA bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (`.`). For example, `/:a-:b`.\n\n### Patches\n\nFor users of 0.1, upgrade to `0.1.10`. For users of 6.0.0, upgrade to `6.3.0`. All other users should upgrade to `8.0.0`.\n\nThese versions add backtrack protection when a custom regex pattern is not provided:\n\n- [0.1.10](https://github.com/pillarjs/path-to-regexp/releases/tag/v0.1.10)\n- [1.9.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v1.9.0)\n- [3.3.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v3.3.0)\n\nThey do not protect against vulnerable user supplied capture groups. Protecting against explicit user patterns is out of scope for this library and not considered a vulnerability.\n\nVersion [6.3.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v6.3.0) removes the features that can cause a ReDoS.\n\nVersion [7.1.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v7.1.0) can enable `strict: true` and get an error when the regular expression might be bad.\n\nVersion [8.0.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v8.0.0) removes the features that can cause a ReDoS.\n\n### Workarounds\n\nAll versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change `/:a-:b` to `/:a-:b([^-/]+)`.\n\nIf paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. For example, halving the attack string improves performance by 4x faster.\n\n### Details\n\nUsing `/:a-:b` will produce the regular expression `/^\\/([^\\/]+?)-([^\\/]+?)\\/?$/`. This can be exploited by a path such as `/a${'-a'.repeat(8_000)}/a`. [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS) has a good example of why this occurs, but the TL;DR is the `/a` at the end ensures this route would never match but due to naive backtracking it will still attempt every combination of the `:a-:b` on the repeated 8,000 `-a`.\n\nBecause JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and can lead to a DoS. In local benchmarks, exploiting the unsafe regex will result in performance that is over 1000x worse than the safe regex. In a more realistic environment using Express v4 and 10 concurrent connections, this translated to average latency of ~600ms vs 1ms.\n\n### References\n\n* [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS)\n* [Detailed blog post](https://blakeembrey.com/posts/2024-09-web-redos/)",
"severity": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P"
}
],
"affected": [
Expand All @@ -29,10 +25,10 @@
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0.2.0"
"introduced": "0"
},
{
"fixed": "1.9.0"
"fixed": "0.1.10"
}
]
}
Expand All @@ -48,10 +44,10 @@
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
"introduced": "0.2.0"
},
{
"fixed": "0.1.10"
"fixed": "1.9.0"
}
]
}
Expand Down Expand Up @@ -94,6 +90,25 @@
]
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "path-to-regexp"
},
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.0.0"
},
{
"fixed": "6.3.0"
}
]
}
]
}
],
"references": [
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