# CVE-2026-42765: openssl: Issue summary: When a partial-chain certificate verification is enabled together with OCSP response checking for the...

CVE-2026-42765 is fixed in openssl on 1 platform by DEBIAN-CVE-2026-42765 (version 3.6.3-1), released June 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-42765
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0051
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 9, 2026

## Description

Issue summary: When a partial-chain certificate verification is enabled together with OCSP response checking for the whole chain, a NULL dereference will happen if the verified chain does not have a self-signed trusted anchor, crashing the process.  Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application.  When performing OCSP response checking for certificates in the verification chain, the code always tries to access the next certificate as the issuer. There is a check for a self-signed certificate. However with the partial chain verification enabled when the chain does not have a self-signed trusted anchor, the issuer will be NULL for the last certificate in the chain. A NULL pointer dereference then happens.  This issue affects only applications which enable both OCSP verification of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial chain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate verification. Both flags are disabled by default. For that reason, we have assigned Low severity to the issue.  No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | openssl Debian 14 | 3.6.3-1 | [DEBIAN-CVE-2026-42765](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42765.md) | Jun 24, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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