Vulnerability in Openssl (CVE-2026-63073)
Summary
Vulnerability in Openssl (CVE-2026-63073). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
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
implem…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-63073 has been found in Openssl.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Openssl CVE-2026-63073" on the vendor's site.
CVE-2026-63073 (Openssl) — CWE-134 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-134) exists in Openssl.
Check the vendor advisory for the affected versions of Openssl.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Openssl' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Openssl' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Opensslを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- patch openssl-security@openssl.org
- patch openssl-security@openssl.org
- patch openssl-security@openssl.org
- patch openssl-security@openssl.org
- patch openssl-security@openssl.org
- web nvd.nist.gov
- web github.com