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CVE-2026-63074

MediumCVSS 5.9 / 10
Published Aug 25, 2026·Last modified Aug 27, 2026
Affected Components(51)
openssl/openssl
openssl-3.6.2
openssl/openssl
3.4-PRE-CLANG-FORMAT-WEBKIT
openssl/openssl
openssl-3.4.0
1 / 17
Description

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.

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Risk Scores
Base Score
5.9

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
5.4

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.56%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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