Client crash via stale OCSP response pointer
Published Jun 9, 2026 · Updated Jun 9, 2026
Double-free in OpenSSL 3.6.0 through 3.6.2 and 4.0.0 allows remote attackers to crash TLS clients via stapled OCSP responses. In check_cert_ocsp_resp(), an unsuccessful response frees OCSP_BASICRESP state without clearing its pointer, so common cleanup frees it again. The default configuration disables OCSP stapling; exploitation requires a client to connect to an attacker-controlled server, and the straightforward consequence is a client crash.
Summary
What happened
Double-free in OpenSSL 3.6.0 through 3.6.2 and 4.0.0 allows remote attackers to crash TLS clients via stapled OCSP responses. In check_cert_ocsp_resp(), an unsuccessful response frees OCSP_BASICRESP state without clearing its pointer, so common cleanup frees it again. The default configuration disables OCSP stapling; exploitation requires a client to connect to an attacker-controlled server, and the straightforward consequence is a client crash.
The record
- CVE
- CVE-2026-35188
- Published
- Jun 9, 2026
- Updated
- Jun 9, 2026
- Vendor
- OpenSSL Project
- Product
- OpenSSL
- Classifications
- CWE-415, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 9, 2026CVE publishedPublication date reported by the CVE source.
- Jun 9, 2026Record 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=3.6.0 <3.6.3
- Affected versionversion=4.0.0 <4.0.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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