CVE-2026-63074

CMP Indefinite Cache Growth of ExtraCerts

Published Aug 25, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4795-1 openssl security update
Debian DSA Debian DSA DSA-6465-1 openssl security update
Ubuntu USN Ubuntu USN USN-8678-1 OpenSSL vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Openssl
Openssl openssl
Vendors & Products Openssl
Openssl openssl
Type Values Removed Values Added
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.
Title CMP Indefinite Cache Growth of ExtraCerts
Weaknesses CWE-770
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
openssl
Published
Updated
Aug 25, 2026, 2:36 PM
Reserved
Jul 15, 2026, 1:10 PM
Status
Analyzed
Published
Aug 25, 2026, 1:19 PM
Modified
Sep 11, 2026, 9:16 PM
Severity
Low
Public date
Aug 25, 2026, 12:00 AM