CVE-2026-63074

Issue summary: The OpenSSL Certificate Management Protocol (CMP) caches

additional certificates (extraCerts) sent in a CMP message, but never expunges

them (for instance if they are invalid). If a server reuses an OSSL_CMP_CTX

frequently, this cache of extraCerts may grow unboundedly, and a malicious

client may flood a CMP server with requests driving this growth.

Impact summary: Users utilizing a CMP server that reuses a single OSSL_CMP_CTX

for the lifetime of a server process may observe unbounded memory growth in the

event a malicious client repeatedly sends requests containing unique extra

certificates, which may lead to OOM conditions.

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: If a remote user sends CMP messages to a server with a list of

extraCerts and the message is rejected, the extraCerts from the message remains

in the server contexts untrusted certificate stack. This exposes servers with

long lived ctx objects to Denial of Service attacks in which an attacker sends

messages intending to be rejected with a large list of additional certificates

repeatedly, forcing the server to store them indefinitely.

The issue was fixed by removing the added extra certs if the message is

rejected, using the same method as when the context is configured to not do

caching at all.

FIPS impact: no

As the CMP code lives outside the FIPS module boundary, no FIPS

modules are affected by this CVE.