SSRF bypass via unvalidated URL passwords
Published Oct 4, 2021 · Updated Sep 17, 2024
Improper URL validation in PHP 7.3 before 7.3.29, 7.4 before 7.4.21, and 8.0 before 8.0.8 allows remote attackers to bypass SSRF checks. php_filter_validate_url validates the parsed username but fails to apply is_userinfo_valid to the parsed password, so backslashes and other invalid password characters are accepted. Exploitation requires an application to trust FILTER_VALIDATE_URL for attacker-controlled URLs; downstream parsers can then contact or select a different host.
Summary
What happened
Improper URL validation in PHP 7.3 before 7.3.29, 7.4 before 7.4.21, and 8.0 before 8.0.8 allows remote attackers to bypass SSRF checks. php_filter_validate_url validates the parsed username but fails to apply is_userinfo_valid to the parsed password, so backslashes and other invalid password characters are accepted. Exploitation requires an application to trust FILTER_VALIDATE_URL for attacker-controlled URLs; downstream parsers can then contact or select a different host.
The record
- CVE
- CVE-2021-21705
- Published
- Oct 4, 2021
- Updated
- Sep 17, 2024
- Vendor
- The PHP Group
- Product
- PHP
- Classifications
- CWE-20, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 4, 2021CVE publishedPublication date reported by the CVE source.
- Sep 17, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=7.3.x <7.3.29
- Affected versionversion=7.4.x <7.4.21
- Affected versionversion=8.0.X <8.0.8
What conditions does exploitation require?
What is affected?
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.
Public exploit references
- PHP bug 81122 crafted-URL proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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