CVE-2026-42765
Description
A flaw was found in OpenSSL. When an application is configured with specific non-default settings for certificate verification, including both Online Certificate Status Protocol (OCSP) response checking and partial chain verification, a NULL dereference can occur. This vulnerability can be triggered if the certificate chain lacks a self-signed trusted anchor, causing the application to crash. This leads to a Denial of Service (DoS) for the affected application.
Statement
This issue is rated as Low impact. A NULL pointer dereference can occur in applications that enable both OCSP response checking for the entire certificate chain and partial chain verification. Since both of these flags are disabled by default in Red Hat products, the risk of exploitation is significantly reduced. This flaw could lead to a Denial of Service if an application is configured with these non-default settings.
Mitigation
To mitigate this issue, 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. These flags are disabled by default, and maintaining the default configuration prevents exposure to this flaw. Consult application-specific documentation for details on how to configure certificate verification flags.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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