# CVE-2026-63074: OpenSSL CMP unbounded certificate cache growth

Source: https://junglewise.ai/threats/cve-2026-63074-openssl-cmp-unbounded-certificate-cache-growth  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-63074 · Severity: medium · CVSS 5.9 · Published 2026-08-25

OpenSSL's Certificate Management Protocol (CMP) feature caches additional certificates sent in CMP messages but fails to clean them up if the message is rejected. A malicious attacker can repeatedly send CMP requests with large lists of invalid extra certificates to a CMP server, forcing it to store them indefinitely and causing the server's memory usage to grow without bounds, eventually leading to out-of-memory errors and service unavailability.

Technologies: [OpenSSL](https://junglewise.ai/threats/technologies/openssl). Vendors: [OpenSSL](https://junglewise.ai/threats/vendors/openssl).

## Quick answers

**Is CVE-2026-63074 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63074 being exploited in the wild.

**How severe is CVE-2026-63074?** Medium severity, with a CVSS score of 5.9, published 25 August 2026.

**Which products and versions are affected?** OpenSSL OpenSSL.

**Is there a fix for CVE-2026-63074?** A patch was published on 2026-08-24: Patches merged as commits 01e5679 and 21a5d96 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63074 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63074?** Check whether you run OpenSSL. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a resource exhaustion flaw (CWE-770) in OpenSSL's CMP implementation where the extraCerts cache in a reused OSSL_CMP_CTX context is never expunged after a message rejection. When a CMP server reuses a single context object across multiple requests, an attacker can send malformed CMP messages with large lists of extraCerts; even though the message is rejected, the certificates remain in the server's untrusted certificate stack. An attacker with network access to a CMP server can exploit this without authentication by repeatedly sending CMP messages with unique extra certificates, causing unbounded memory growth. The fix, applied in commits 01e5679 and 21a5d96, removes cached extra certificates when a message is rejected, treating rejected messages the same as when caching is disabled.

## Affected products

- OpenSSL OpenSSL

## Timeline

- 2026-08-25: disclosed
- 2026-08-24: patched: Patches merged as commits 01e5679 and 21a5d96

## References

- [https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7](https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7)
- [https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f](https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f)

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