CMP Indefinite Cache Growth of ExtraCerts (CVE-2026-63074)

What is affected, what to do

A flaw was found in OpenSSL. The CMP (Certificate Management Protocol) implementation does not clear cached additional certificates when an invalid message is received, leading to excessive memory consumption.

Update OpenSSL to version 4.0.2, OpenSSL to version 3.6.4, OpenSSL to version 3.5.8.

Affected

• OpenSSL lt 4.0.0..4.0.2
• OpenSSL lt 3.6.0..3.6.4
• OpenSSL lt 3.5.0..3.5.8
• OpenSSL lt 3.4.0..3.4.7
• OpenSSL lt 3.0.0..3.0.22

Fixed in

• OpenSSL 4.0.2
• OpenSSL 3.6.4
• OpenSSL 3.5.8
• OpenSSL 3.4.7
• OpenSSL 3.0.22

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Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in OpenSSL. The CMP (Certificate Management Protocol) implementation does not clear cached additional certificates when an invalid message is received, leading to excessive memory consumption. This allows a malicious client to repeatedly send requests containing unique extra certificates to cause memory exhaustion, eventually resulting in a denial of service.

Source: redhat_csaf, Debian Security Advisories, Ubuntu Security Notices, suse_csaf, Debian LTS Advisories, BSI WID Portal, BSI CSAF, NVD (NIST), cvelistv5, Microsoft Security Update Guide

Vendors and products

• Debian Openssl
• Freebsd Project Freebsd OS
• Meinberg Lantime
• Open Source Openssl
• OpenSSL OpenSSL
• Ubuntu Openssl

Weakness classes (CWE)

• CWE-770Allocation of Resources Without Limits or Throttling

  Base

  The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

  Entry at MITRE CWE-770

References & sources

• openssl-library.orgOpenSSL AdvisoryVendor advisory
• github.com4.0.2 git commitPatch
• github.com3.6.4 git commitPatch
• github.com3.5.8 git commitPatch
• github.com3.4.7 git commitPatch
• github.com3.0.22 git commitPatch

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 11.09.2026Initial analysis by NVDNVD

   Newly listed as affected:

   • OpenSSL (3.5.0 – before 3.5.8; 3.6.0 – before 3.6.4; 4.0.0 – before 4.0.2; 3.4.0 – before 3.4.7; 3.0.0 – before 3.0.22)

   New references:

   • https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7
   • https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f
   • https://github.com/openssl/openssl/commit/74ae7f6df47a5767c1010b88c47507dfc5b32c46
   • https://github.com/openssl/openssl/commit/75360af9650d4e0c82ba0050c5c9912cd79e54af

   and 2 more references

   Show 7 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Product configuration	added	—	OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.8 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.4 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.2 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.7 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.22
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7 Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/74ae7f6df47a5767c1010b88c47507dfc5b32c46 Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/75360af9650d4e0c82ba0050c5c9912cd79e54af Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/f636f9ca0fa1bae5b42f9e787f025c96fb09c43a Types: Patch
   Reference type	added	—	OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260825.txt Types: Vendor Advisory

   Source identifier: nvd@nist.gov

2. 25.08.2026Record modifiedCISA ADP

   CVSS V3.1: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

   CISA assessment (SSVC): exploitation: none known, automatable: no

   Show 2 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
   SSVC assessment	added	—	{"id":"CVE-2026-63074","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-08-25T14:36:10.702053Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

3. 25.08.2026Receivedopenssl.org

   Weakness type: CWE-770

   Description added or changed

   New references:

   • https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7
   • https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f
   • https://github.com/openssl/openssl/commit/74ae7f6df47a5767c1010b88c47507dfc5b32c46
   • https://github.com/openssl/openssl/commit/75360af9650d4e0c82ba0050c5c9912cd79e54af

   and 2 more references

   Show 9 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Affected versions (publisher)	added	—	OpenSSL
   Description	added	—	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.
   Weakness type (CWE)	added	—	CWE-770
   Reference	added	—	https://github.com/openssl/openssl/commit/01e567978a55fba18142a230380c31296049fae7
   Reference	added	—	https://github.com/openssl/openssl/commit/21a5d9658b0c66daace60e10ea18ff32a448de9f
   Reference	added	—	https://github.com/openssl/openssl/commit/74ae7f6df47a5767c1010b88c47507dfc5b32c46
   Reference	added	—	https://github.com/openssl/openssl/commit/75360af9650d4e0c82ba0050c5c9912cd79e54af
   Reference	added	—	https://github.com/openssl/openssl/commit/f636f9ca0fa1bae5b42f9e787f025c96fb09c43a
   Reference	added	—	https://openssl-library.org/news/secadv/20260825.txt

   Source identifier: openssl-security@openssl.org