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NVD / CVE Program· CNA openssl

CVE-2026-63073: Untrusted Sender DN Used as Format String in CMP Response Validation

Noroxi assessment

Priority: Monitor (action score 39/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 66.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: OpenSSL OpenSSL 3.4.7, 3.5.8, 3.6.4; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-6.

Low priority for now. Upgrade to OpenSSL OpenSSL 3.4.7, 3.5.8, 3.6.4; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-6 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Aug 25, 2026
Updated
Sep 11, 2026
EPSS
1.1% · 66th percentile

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.1%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-63073

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
opensslopenssl

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • openssl openssl3.4.0 and later · before 3.4.7
  • openssl openssl3.5.0 and later · before 3.5.8
  • openssl openssl3.6.0 and later · before 3.6.4
  • openssl openssl4.0.0 and later · before 4.0.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (openssl). Independent of NVD's CPE analysis and usually ahead of it.

  • OpenSSL OpenSSL

    • 4.0.0 and later · before 4.0.2affected · semver
    • 3.6.0 and later · before 3.6.4affected · semver
    • 3.5.0 and later · before 3.5.8affected · semver
    • 3.4.0 and later · before 3.4.7affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10opensslbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-develbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-libsbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-perlbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:9opensslbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-develbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-libsbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-perlbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Alpine:v3.21opensslfrom 3.4.0 · before 3.3.7-r13.3.7-r1
Alpine:v3.22opensslfrom 3.4.0 · before 3.5.8-r03.5.8-r0
Debian:13opensslbefore 3.5.7-1~deb13u23.5.7-1~deb13u2
Debian:14opensslbefore 3.6.4-13.6.4-1
openSUSE:Leap 16.0openssl-3before 3.5.0-160000.10.13.5.0-160000.10.1
openSUSE:Tumbleweedopenssl-3before 3.5.3-8.13.5.3-8.1
Red Hat:enterprise_linux:10.2opensslbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-debuginfobefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-debugsourcebefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-develbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-libsbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-libs-debuginfobefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-perlbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:9::appstreamopenssl-debuginfobefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Red Hat:enterprise_linux:9::appstreamopenssl-debugsourcebefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Red Hat:enterprise_linux:9::appstreamopenssl-develbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8

+8

Same product

openssl: all records

Other highest-scoring records for the same primary product.

  • CVE-2014-0160The (1) TLS and (2) DTLS implementations in OpenSSL 1.0.1 before 1.0.1g do not properly handle Heartbeat Extension packets, which allows remKEV
    90Now
  • CVE-2021-3711SM2 Decryption Buffer Overflow
    65This week
  • CVE-2003-0545Double free vulnerability in OpenSSL 0.9.7 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code
    65This week

Published before and after this one in the same product

  • ← EarlierCVE-2026-54874Aug 25, 2026 · Excessive Memory Use Buffering DTLS Records for a Future Epoch
    30Monitor
  • ← EarlierCVE-2026-63072Aug 25, 2026 · Heap Buffer Overflow in CMS Key Unwrapping
    30Monitor
  • Later →CVE-2026-63074Aug 25, 2026 · CMP Indefinite Cache Growth of ExtraCerts
    23Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
OpenSSL OpenSSL3.4.7Vendor (CNA)
OpenSSL OpenSSL3.5.8Vendor (CNA)
OpenSSL OpenSSL3.6.4Vendor (CNA)
OpenSSL OpenSSL4.0.2Vendor (CNA)
azl3 openssl 3.3.7-6 on Azure Linux 3.03.3.7-6Microsoft (MSRC)
almalinux:openssl1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-devel1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-libs1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-perl1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
alpine:openssl3.3.7-r1 · Alpine:v3.21Package registry (OSV)
debian:openssl3.5.7-1~deb13u2 · Debian:13Package registry (OSV)
opensuse:openssl-33.5.3-8.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:openssl1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-debuginfo1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-debugsource1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-devel1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-libs1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-libs-debuginfo1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-perl1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
rocky linux:openssl1:3.5.8-1.el10_2 · Rocky Linux:10Package registry (OSV)
suse:openssl-33.5.0-160000.10.1 · SUSE:Linux Micro 6.2Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days+1% in 7 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-134 · Use of Externally-Controlled Format String

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records