CVE-2026-42765
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BaseFortify

Publication date: 2026-06-09

Last updated on: 2026-06-09

Assigner: OpenSSL Software Foundation

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.
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Meta Information
Published
2026-06-09
Last Modified
2026-06-09
Generated
2026-06-10
AI Q&A
2026-06-09
EPSS Evaluated
N/A
NVD
CVE-2026-42765
EUVD
EUVD-2026-35482
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
openssl openssl *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.
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Compliance Impact

This vulnerability causes a denial of service by crashing the application due to a NULL pointer dereference when certain certificate verification flags are enabled.

However, there is no information provided about its direct impact on compliance with common standards and regulations such as GDPR or HIPAA.

Executive Summary

This vulnerability occurs when an application enables both partial-chain certificate verification and OCSP response checking for the entire certificate chain. If the verified chain does not include a self-signed trusted anchor certificate, the process attempts to access a NULL issuer certificate, causing a NULL pointer dereference and crashing the process.

Specifically, during OCSP response checking, the code tries to access the next certificate as the issuer. Although there is a check for a self-signed certificate, with partial chain verification enabled and no self-signed trusted anchor present, the issuer pointer becomes NULL for the last certificate, leading to the crash.

Impact Analysis

The vulnerability can cause a NULL pointer dereference that triggers a crash of the application performing certificate verification. This results in a Denial of Service (DoS), making the application unavailable or unstable.

Mitigation Strategies

To mitigate this vulnerability, ensure that applications do not enable both OCSP verification of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial chain verification (X509_V_FLAG_PARTIAL_CHAIN) simultaneously, as both flags are disabled by default.

If your application requires these features, consider disabling partial chain verification or OCSP response checking until a patch or update addressing this issue is available.

Additionally, monitor for application crashes that may indicate a NULL pointer dereference caused by this issue.

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