CVE-2026-42764
Description
A flaw was found in the OpenSSL QUIC (Quick UDP Internet Connections) server. A remote attacker could send a specially crafted QUIC initial packet with an invalid token. If the server's address validation is explicitly disabled, this could lead to a NULL pointer dereference, causing the server process to terminate abnormally and resulting in a Denial of Service (DoS).
Statement
This is a Moderate severity issue. A NULL pointer dereference can occur in the OpenSSL QUIC server when processing initial packets with invalid tokens, leading to a denial of service. This vulnerability is only exploitable if the client address validation is explicitly disabled using the SSL_LISTENER_FLAG_NO_VALIDATE flag, which is not the default configuration for OpenSSL QUIC servers.
Mitigation
To mitigate this issue, ensure that the OpenSSL QUIC server has client address validation enabled. This is the default configuration. If the `SSL_LISTENER_FLAG_NO_VALIDATE` flag is being used with the `SSL_new_listener()` call, it should be removed to prevent the vulnerability from being exploitable.
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).
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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