Client hang via basic-auth regex backtracking
Published Jan 30, 2020 · Updated Aug 4, 2024
Regular expression denial of service in Python allows remote attackers controlling an HTTP server to hang an authenticating client. The AbstractBasicAuthHandler parser applies a regex whose nested repetition lets commas match overlapping paths, causing exponential backtracking on a crafted authentication header. Reachability requires the client to contact the attacker-controlled server and process its HTTP 401 or proxy 407 basic-authentication challenge; the bounded consequence is a client-side hang.
Summary
What happened
Regular expression denial of service in Python allows remote attackers controlling an HTTP server to hang an authenticating client. The AbstractBasicAuthHandler parser applies a regex whose nested repetition lets commas match overlapping paths, causing exponential backtracking on a crafted authentication header. Reachability requires the client to contact the attacker-controlled server and process its HTTP 401 or proxy 407 basic-authentication challenge; the bounded consequence is a client-side hang.
The record
- CVE
- CVE-2020-8492
- Published
- Jan 30, 2020
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-400, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 30, 2020CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- AbstractBasicAuthHandler crafted-header reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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