Medium
Security advisory
There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-3733
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 11:50 UTC · Revision 1
Source evidence
There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.
osv:CVE-2021-3733
Complete source record
{
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"modified": "2026-10-20T10:54:49.105547294Z",
"provider": "osv",
"references": [
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"source_id": "core-osv",
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"published_at": "2022-03-10T17:42:59.623+00:00"
}