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Fencer Intel
critical 9.8

CVE-2026-63073 in the critical feed json

Untrusted Sender DN Used as Format String in CMP Response Validation

published 2mo ago modified last mo. also EUVD-2026-65483

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits
0
none known

Summary

Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to `ERR_raise_data()`.

Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client that enforces an expected sender or uses a pinned server certificate whose subject becomes the default expected sender.

CWE: CWE-134 (Use of Externally-Controlled Format String)

Description: When validating a received CMP message, ossl_cmp_msg_check_update() converts the peer-supplied sender distinguished name with X509_NAME_oneline() and passes it directly as the format argument to ERR_raise_data(). Percent characters survive the conversion, so a sender DN such as "CN=%s%n" reaches BIO_vsnprintf() as an attacker-controlled format string with no matching variadic arguments. This path is only reached when the caller configures an expected sender or pins a server certificate, which is the normal configuration for a CMP client validating server responses.

Since the attacker controls the format string but none of the variadic arguments, such specifiers as %s and %n dereference or write through unrelated stack contents and crash the client. The reliable consequence is a denial of service, when the response comes from a malicious or intercepted CMP endpoint. There is no controlled memory write, arbitrary-address read, or reliable path to remote code execution.

FIPS impact: no

No FIPS modules are affected by this issue, as the CMP protocol implementation is outside the OpenSSL FIPS module boundary.

Patch / fix

  • OpenSSL OpenSSL 3.4.7, 3.5.8, 3.6.4, 4.0.2
  • openssl Debian 13 3.5.7-1~deb13u2
  • openssl Debian 14 3.6.4-1

debian advisories DEBIAN-CVE-2026-63073

  • openssl Ubuntu 26.04 LTS 3.5.5-1ubuntu3.4

ubuntu advisories UBUNTU-CVE-2026-63073

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl RHEL 9 1:3.5.8-1.el9_8
  • openssl-libs RHEL 9 1:3.5.8-1.el9_8
  • openssl-perl RHEL 9 1:3.5.8-1.el9_8
  • openssl RHEL 10.2 1:3.5.8-1.el10_2
  • openssl-libs RHEL 10.2 1:3.5.8-1.el10_2
  • openssl-perl RHEL 10.2 1:3.5.8-1.el10_2
  • openssl3 hummingbird 1 3.5.8-0.1.hum1
  • openssl3-libs hummingbird 1 3.5.8-0.1.hum1

red hat advisories RHSA-2026:67165RHSA-2026:67154RHSA-2026:59635RHSA-2026:59641

  • openssl-3 SLE Module for Basesystem 15 SP7 3.5.0-150700.5.50.1
  • openssl-3 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.5.0-160000.10.1

suse advisories SUSE-SU-2026:4039-1SUSE-SU-2026:23463-1SUSE-SU-2026:23609-1

  • openssl-3 openSUSE Leap 16.0 3.5.0-160000.10.1
  • openssl-3 openSUSE Tumbleweed 3.5.3-8.1

opensuse advisories openSUSE-SU-2026:21744-1openSUSE-SU-2026:11623-1

  • openssl AlmaLinux 10 1:3.5.8-1.el10_2.alma.1
  • openssl-libs AlmaLinux 10 1:3.5.8-1.el10_2.alma.1
  • openssl-perl AlmaLinux 10 1:3.5.8-1.el10_2.alma.1
  • openssl AlmaLinux 9 1:3.5.8-1.el9_8
  • openssl-libs AlmaLinux 9 1:3.5.8-1.el9_8
  • openssl-perl AlmaLinux 9 1:3.5.8-1.el9_8

almalinux advisories ALSA-2026:67154ALSA-2026:67165

  • openssl Rocky Linux 9 1:3.5.8-1.el9_8
  • openssl Rocky Linux 10 1:3.5.8-1.el10_2

rocky linux advisories RLSA-2026:67165RLSA-2026:67154

  • openssl Alpine 3.21 3.3.7-r1
  • openssl Alpine 3.24, Alpine 3.23, Alpine 3.22 3.5.8-r0

alpine advisories ALPINE-CVE-2026-63073

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl Azure Linux 3.0 3.3.7-6

azure linux advisories AZL-97950

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-63073 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63073 updated cvss 5.9

openssl: untrusted sender DN used as format string in CMP response validation

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Enterprise Linux 10 edk2 Red Hat JBoss Core Services jbcs-httpd24-openssl, jbcs-httpd24-openssl-libs, jbcs-httpd24-openssl-perl, jbcs-openssl-win6-x86_64.zip 3.5.5-SP4 Red Hat JBoss Web Server 6 jws-optional-native-components-win6-x86_64.zip 6.2.4.ER1 Red Hat JBoss Web Server 7 jws-optional-native-components-win6-x86_64.zip 6.2.4.ER1 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9
    +1 more products
    Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/cert-manager-operator-rhel9 1790272426, cert-manager/cert-manager-operator-rhel9 1790589855, cert-manager/jetstack-cert-manager-rhel9 1790223279, cert-manager/jetstack-cert-manager-rhel9 1790589912, cert-manager/cert-manager-istio-csr-rhel9 1790223719, cert-manager/cert-manager-istio-csr-rhel9 1790589914, +1 more
    fixed: vendor fix RHSA-2026:72475
  • Red Hat Enterprise Linux AppStream (v. 9) openssl-perl 3.5.8-1.el9_8
    fixed: vendor fix RHSA-2026:67165
  • Red Hat Enterprise Linux AppStream (v. 10) openssl-perl 3.5.8-1.el10_2
    fixed: vendor fix RHSA-2026:67154
  • Red Hat Enterprise Linux BaseOS (v. 9) openssl 3.5.8-1.el9_8, openssl-libs 3.5.8-1.el9_8
    fixed: vendor fix RHSA-2026:67165
  • Red Hat Enterprise Linux BaseOS (v. 10) openssl 3.5.8-1.el10_2, openssl-libs 3.5.8-1.el10_2
    fixed: vendor fix RHSA-2026:67154
  • Red Hat Hardened Images openssl 3.5.8-0.1.hum1, openssl3 3.5.8-0.1.hum1, openssl-libs 3.5.8-0.1.hum1, openssl-perl 3.5.8-0.1.hum1, openssl3-libs 3.5.8-0.1.hum1, openssl-config-fips 3.5.8-0.1.hum1, +3 more
    fixed: vendor fix RHSA-2026:59641
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1790241954, rhui5/rhua-rhel9 1790242004, rhui5/haproxy-rhel9 1790241900, rhui5/installer-rhel9 1789482961, rhui5/cds-kubernetes-rhel9 1789479916
    fixed: vendor fix RHSA-2026:67956
show 1 more
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/jetstack-cert-manager-acmesolver-rhel9 1790223630 Red Hat Enterprise Linux 6 openssl, openssl-perl Red Hat Enterprise Linux 7 ovmf, OVMF, shim, AAVMF, mokutil, openssl, +5 more Red Hat Enterprise Linux 8 edk2, shim, openssl, shim-x64, edk2-ovmf, shim-aa64, +10 more Red Hat Enterprise Linux 9 edk2, shim, shim-x64, edk2-ovmf, shim-aa64, edk2-tools, +4 more Red Hat Enterprise Linux 10 shim, shim-unsigned-x64, shim-unsigned-aarch64
    +6 more products
    Red Hat Hardened Images unbound Red Hat OpenShift AI (RHOAI) rhoai/odh-llama-stack-k8s-operator-rhel9 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8 Red Hat Satellite 6 puppet-agent, openvox-agent Red Hat Satellite Client puppet-agent, openvox-agent Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1789479900, rhui5/rhua-rhel9 1789478095, rhui5/haproxy-rhel9 1789479891, rhui5/installer-rhel9 1790241922, rhui5/cds-kubernetes-rhel9 1790241897
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
2mo ago

Exploit prediction

1.16% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • OpenSSL OpenSSL

Classification

Weakness
  • CWE-134 Use of Externally-Controlled Format String
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.