CVE-2021-3450 — CA certificate check bypass with X509_V_FLAG_X509_STRICT

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Fedoraproject Fedora, Freebsd Freebsd, Mcafee Web Gateway…).
2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
3. Apply the fixed version or the patch documented under Remediation.
4. EPSS ahead of 97% of scored CVEs: prioritize it in the patch queue.
5. Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-295 · Improper Certificate Validation

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 18.34%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
• Check TLS negotiations and unexpected certificates in the component’s traffic.

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · openssl/openssl
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• Fix documented
  Oct 13, 2026 · NIST National Vulnerability Database
• CVSS changed · 7.4
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Modified
  Oct 13, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 13, 2026 · NIST National Vulnerability Database
• 2021
• CVE published
  Mar 25, 2021 · openssl

Source activity

Repeated readings are counted rather than listed.

• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

24 on the record

• mta.openssl.org/pipermail/openssl-announce/2021-March/000198.html
  Mailing List, Vendor Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.openssl.org/news/secadv/20210325.txt
  Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpuoct2021.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpujul2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpuapr2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpuApr2021.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com//security-alerts/cpujul2021.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• kc.mcafee.com/corporate/index
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• security.gentoo.org/glsa/202103-03
  Third Party Advisory, vendor-advisory, x_refsource_GENTOO, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/03/28/4
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• www.tenable.com/security/tns-2021-09
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBF
  vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.asc
  Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/03/28/3
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• git.openssl.org/gitweb/
  x_refsource_CONFIRM, NIST National Vulnerability Database
• security.netapp.com/advisory/ntap-20210326-0006/
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-G
  Third Party Advisory, vendor-advisory, x_refsource_CISCO, NIST National Vulnerability Database
• kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.tenable.com/security/tns-2021-08
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/03/27/1
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• www.tenable.com/security/tns-2021-05
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.openwall.com/lists/oss-security/2021/03/27/2
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• High CVE-2026-103946 SQL Injection 1d
• High CVE-2026-84784 QUIC: Unbounded RETIRE_CONNECTION_ID Backlog 16d
• High CVE-2026-84783 Use-After-Free in X.509 Extension Cache Under Concurrent Use 16d
• High CVE-2026-84782 DTLS Retransmits Handshake Messages From a Stale Buffer Offset 16d
• Low CVE-2026-77696 Timing Side-Channel in SM2 Signature Generation 16d
• Medium CVE-2026-75805 NULL Pointer Dereference in CMP Client Revocation Response Handling 16d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-3450 is "CA certificate check bypass with X509_V_FLAG_X509_STRICT", rated High. It affects Fedora (Fedoraproject); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.4 describes technical severity. EPSS 18.34% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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