OpenSSL OCSP Stapling Verification Double Free Remote Code Execution Vulnerability

July 15th, 2026
ZDI-26-425 ZDI-CAN-30391

CVE ID

CVE-2026-35188

CVSS Score

7.5 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected Vendors

OpenSSL

Affected Products

OpenSSL

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of OpenSSL. User interaction is required to exploit this vulnerability in that the target must make a request to a malicious server.

The specific flaw exists within the processing of malformed OCSP responses. The issue results from the lack of validating the existence of an object prior to performing further free operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process.

Additional Details

OpenSSL has issued an update to correct this vulnerability. More details can be found at:
https://openssl-library.org/news/vulnerabilities/#CVE-2026-35188

Disclosure Timeline

  • 2026-04-16 - Vulnerability reported to vendor
  • 2026-07-15 - Coordinated public release of advisory
  • 2026-07-15 - Advisory Updated

Credit

TrendAI Zero Day Initiative

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