CVE-2026-63073

Aliases:DEBIAN-CVE-2026-63073UBUNTU-CVE-2026-63073ALPINE-CVE-2026-63073CGA-2r65-2whv-vg9fCGA-6r5h-8fv2-r4fcCGA-7g9v-fwv3-968rCGA-867p-85m2-g3pfCGA-9g9c-34mf-x8vvCGA-9wpw-9gpf-8vgfCGA-f99f-p537-f846CGA-gj86-7hr7-fwf9CGA-jhmg-989j-q2vgCGA-mq4q-fmrg-3c8rCGA-p7jc-jw86-5h4wCGA-r2m6-mcr2-wq38CGA-v92x-7m68-999qCGA-wf7j-jh94-xg9c
Advisory lineage Upstream: 0 Downstream: 10
Analyzed
Published: 25 Aug 2026, 12:59
Last modified:31 Aug 2026, 19:12

Vulnerability Summary

Overall Risk (default)
high
70/100
CVSS Score
9.8 CRITICAL
v3.1 (cve.org)
EPSS Score
0.93% LOW
1% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

25 Aug 2026, 12:59
Published
Vulnerability first disclosed
31 Aug 2026, 19:12
Last Modified
Vulnerability information updated

Description

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.

CVSS Metrics

  • v3.1•CRITICAL•Score: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.93%• Percentile: 59%

Techniques & Countermeasures

  • CWE-134•Use of Externally-Controlled Format String

    The product uses a function that accepts a format string as an argument, but the format string originates from an external source.

Affected Systems

  • alpine•openssl

    < 3.5.8-r0 | < 3.5.8-r0 | < 3.5.8-r0 | ≥ 3.4.0, < 3.3.7-r1 | ≥ 3.4.0, < 3.5.8-r0 | ≥ 3.4.0, < 3.5.8-r0 | ≥ 3.4.0, < 3.5.8-r0

  • chainguard•eco-python-openssl-4

    all | < 4.0.2-r0

  • chainguard•eco-python-openssl-4-pyca

    all | < 4.0.2-r0

  • chainguard•eco-python-openssl-4-pyca-dev

    all | < 4.0.2-r0

  • chainguard•openssl-provider-fips-3.4.0

    all | < 0

  • chainguard•openssl-provider-fips-3.4.0-dbg

    all

  • chainguard•openssl-provider-fips-3.6.0

    all

  • chainguard•openssl-provider-fips-3.6.0-dbg

    all | < 0

  • debian•openssl

    all | < 3.5.7-1~deb13u2 | < 3.6.4-1

  • ubuntu•edk2

    all

  • ubuntu•edk2-hwe

    all

  • ubuntu•nodejs

    all

  • ubuntu•openssl

    < 3.5.5-1ubuntu3.4

  • ubuntu•openssl-fips

    all

  • openssl•openssl

    ≥ 3.4.0, < 3.4.7 | ≥ 3.5.0, < 3.5.8 | ≥ 3.6.0, < 3.6.4 | ≥ 4.0.0, < 4.0.2

References (12)