CVE-2026-42769 Trust-Anchor Substitution via cert/issuer Typo in CMP rootCaKeyUpdate
A typo in OpenSSL's CMP root CA key update verification allows a Registration Authority to substitute the root CA trust anchor, escalating privileges to root CA level.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42769?
CVE-2026-42769 is a medium-severity authentication bypass vulnerability in Openssl Openssl, published on 9 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Issue Summary: An error in the callback used to verify the certificate provided in a Root CA key update Certificate Management Protocol (CMP) message response rendered the certificate validation ineffectual, which could lead to escalation of credentials from the Registration Authority (RA) level to the root Certification Authority (root CA) level.
Impact Summary: The Registration Autority could replace the root CA certificate for the CMP clients with an arbitrary root CA certificate.
One of the parts of the Certificate Management Protocol (CMP), specified in RFC 9810, is Root Certification Authority (root CA) key Rollover, which is sent by the server in a message with type 'id-it-rootCaKeyUpdate'. As part of these messages, 'newWithOld' certificate, the new root CA certificate signed with the old root CA key, is provided, and verifying its signature is crucial for transferring the trust from the old CA key to the new one.
The 'id-it-rootCaKeyUpdate' messages are expected to be processed with OSSL_CMP_get1_rootCaKeyUpdate(), that is expected to verify the 'newWithOld' certificate. A typo in the certificate chain building code led to adding an incorrect certificate ('newWithOld' instead of 'oldRoot') to the certificate chain, rendering the certificate verification process ineffectual (only the issuer name and the algorithm OIDs were verified by other parts of the verification code).
An attacker who already has credentials that satisfy the CMP message protection checks can generate a new key pair and use a crafted self-signed certificate in its 'id-it-rootCaKeyUpdate' CMP messages which affected CMP clients would accept as a new trust anchor.
Significant preconditions for the attack (having valid RA-level credentials) are the reason the issue was assigned Low severity.
The FIPS modules are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Weakness: CWE-295
Which versions are affected by CVE-2026-42769?
It affects 1 product.
Products include Openssl Openssl.
How do I fix CVE-2026-42769?
Apply the vendor's patch.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-42769 being exploited?
There is no known exploitation of CVE-2026-42769 in the wild and no public exploit code.
Other vulnerabilities in Openssl Openssl
Sources
Also known as ALPINE-CVE-2026-42769, AZL-92840, BELL-CVE-2026-42769, CLSA-2026-1782386492, DEBIAN-CVE-2026-42769, GHSA-rpj2-p5pj-r33v and 3 more.