TLS peer spoofing via partial IDN wildcards
Published May 26, 2023 · Updated Jan 15, 2025
Improper certificate validation in curl 7.12.0 through 8.0.1 allows remote attackers to spoof TLS peers via partial IDN wildcards. The private hostname matcher accepts certificate Subject Alternative Name patterns such as x* against punycode names beginning xn-- instead of rejecting partial wildcards. The flaw affects OpenSSL, Schannel, or Gskit builds and requires a trusted certificate bearing such a pattern, allowing attacker-controlled content to pass TLS identity checks.
Summary
What happened
Improper certificate validation in curl 7.12.0 through 8.0.1 allows remote attackers to spoof TLS peers via partial IDN wildcards. The private hostname matcher accepts certificate Subject Alternative Name patterns such as x* against punycode names beginning xn-- instead of rejecting partial wildcards. The flaw affects OpenSSL, Schannel, or Gskit builds and requires a trusted certificate bearing such a pattern, allowing attacker-controlled content to pass TLS identity checks.
The record
- CVE
- CVE-2023-28321
- Published
- May 26, 2023
- Updated
- Jan 15, 2025
- Vendor
- curl
- Product
- curl
- Classifications
- CWE-295, T1557
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 26, 2023CVE publishedPublication date reported by the CVE source.
- Jan 15, 2025Record 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=Fixed in 8.1.0
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
- Public HackerOne proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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