CVE-2026-75805
Description
A flaw was found in OpenSSL. When a Certificate Management Protocol (CMP) client requests certificate revocation using a PKCS#10 Certificate Signing Request (CSR), it omits the certificate issuer name and serial number. A malicious or compromised CMP server, or an attacker possessing valid message protection credentials, can exploit this flaw by returning a crafted revocation response. This triggers a NULL pointer dereference when the client attempts to compare response data, causing the client application to crash and resulting in a Denial of Service (DoS).
Statement
This flaw is rated Moderate. It is a Denial of Service only: a CMP client can crash when processing a crafted certificate revocation response after requesting revocation with a PKCS#10 CSR. Exploitation requires a malicious or compromised CMP server, or a man-in-the-middle that already has the CMP message-protection secret. There is no confidentiality or integrity impact, FIPS modules are not affected, and clients that identify the certificate by certificate or by issuer and serial number are not affected.
Mitigation
Do not revoke certificates over CMP by supplying a PKCS#10 CSR (`openssl cmp -cmd rr -csr ...` or `OSSL_CMP_CTX_set1_p10CSR()`). Identify the certificate by certificate or by issuer name and serial number instead. Restrict CMP clients to trusted CMP servers and protect CMP message-protection credentials. If CMP certificate revocation is unused, avoid enabling CMP client revocation workflows.
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 | 5.3 |
| 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 | Low |
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:L
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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