CVE-2026-75805 NULL Pointer Dereference in CMP Client Revocation Response Handling
A malicious CMP server can cause a denial of service in OpenSSL clients using PKCS#10 CSRs for revocation by triggering a NULL pointer dereference.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-75805?
CVE-2026-75805 is a medium-severity vulnerability in Openssl Openssl, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Issue summary: A CMP client that requests certificate revocation on the basis of a PKCS#10 CSR may dereference a NULL pointer and terminate abnormally when processing a crafted revocation response.
Impact summary: The NULL pointer dereference happens on a read which leads to a crash and a Denial of Service for the affected client application.
CWE: CWE-476: NULL-pointer dereference
Description: A CMP client revoking a certificate has to tell the server which certificate to revoke, and may do so by supplying a PKCS#10 CSR instead of the certificate itself or its issuer name and serial number. This is 'openssl cmp -cmd rr -csr <file>' on the command line, or OSSL_CMP_exec_RR_ses() with the certificate supplied via OSSL_CMP_CTX_set1_p10CSR() through the API.
A CSR does not contain the issuer name and serial number of the certificate, so the client does not send them. A server may optionally name the certificate it revoked in its response, and the client then compares that name against what it sent. Having sent neither an issuer name nor a serial number, it has nothing to compare against, and a server returning a specially crafted name causes the client to read from a NULL pointer and crash.
The revocation response is checked for valid message protection before the affected code is reached, so an attacker must be a malicious or compromised CMP server, or a man-in-the-middle in possession of the secret used for message protection. Clients that identify the certificate to be revoked by a certificate or by issuer and serial number rather than by a PKCS#10 CSR are not affected.
FIPS impact: no No FIPS modules are affected by this issue, as the CMP protocol implementation is outside the OpenSSL FIPS module boundary.
Weakness: CWE-476
Which versions are affected by CVE-2026-75805?
It affects 1 product.
Products include Openssl Openssl.
How do I fix CVE-2026-75805?
Apply the vendor's patch.
Is CVE-2026-75805 being exploited?
There is no known exploitation of CVE-2026-75805 in the wild and no public exploit code.
Other vulnerabilities in Openssl Openssl
Sources
Also known as ALPINE-CVE-2026-75805, AZL-105369, AZL-105438, AZL-105477, AZL-105528, AZL-105591 and 11 more.