Hostname spoofing via backslash parsing mismatch
Published Feb 21, 2021 · Updated Aug 3, 2024
Improper URL parsing in url-parse before 1.5.0 allows remote attackers to spoof a hostname via backslashes after the protocol. The extractProtocol parser recognizes only forward slashes as the authority delimiter, so a browser-valid backslash sequence is classified as a relative path with no hostname. Exposure depends on a consuming application validating attacker-controlled URLs with the library; the mismatch enables allowlist bypass, SSRF, or open redirects.
Summary
What happened
Improper URL parsing in url-parse before 1.5.0 allows remote attackers to spoof a hostname via backslashes after the protocol. The extractProtocol parser recognizes only forward slashes as the authority delimiter, so a browser-valid backslash sequence is classified as a relative path with no hostname. Exposure depends on a consuming application validating attacker-controlled URLs with the library; the mismatch enables allowlist bypass, SSRF, or open redirects.
The record
- CVE
- CVE-2021-27515
- Published
- Feb 21, 2021
- Updated
- Aug 3, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-20
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 21, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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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
- Backslash URL parsing proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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