CVE-2021-3450
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CA certificate check bypass with X509_V_FLAG_X509_STRICT
rank 47 = 18 + 19 + 0 + 10 + 0
rank@v1 · this cycle
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.18339 · without this subject the record ranks 29
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 7.4, from NVD · without this subject the record ranks 28
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 47
How much of the world it touches
NVD CPE configurations
20 products in the CPE ranges · without this subject the record ranks 37
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 47
$807,000 = $4.99M incident cost x 0.8814887365328109 exposure x 0.18339 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
This record is one instance of CWE-295, improper certificate validation. The index holds 1581 prior instances of this class, 5 KEV-listed. The nearest of its KEV-listed records are drawn beside this. taxonomy@v1
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Harm, if it fires from the vector and the weakness
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Proof-of-concept published · 1 public repository, 2026-06-23.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published · 1 public repository2026-06-23receipt
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 20 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. receipt
Read the rest of the CNA's description
If a "purpose" has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named "purpose" values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j).
NVD's analysis a second authority
- severity
- 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- weakness
- CWE-295
- affected versions
- openssl >= 1.1.1h < 1.1.1k; freebsd 12.2; windriver linux 17.0; and 17 more, listed in full below
check it yourself openssl.org git.openssl.org tools.cisco.com openwall.com openwall.com openwall.com +14 morereceipt
Dated events
Movement the material steps
Show all 75 observations
75 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The pattern, elsewhere
This record is one instance of CWE-295, improper certificate validation. The index holds 1581 prior instances of this class, 5 KEV-listed. The nearest of its KEV-listed records are drawn beside this. [email protected]
"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1
1581 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.
No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.
Siblings and hubs
Records related to this one
No record cites this identifier and it carries no alias. Its defect family is below.
Its defect family
openssl
Of the 8 records in this family that state one, this holds the highest EPSS percentile: 0.97027.
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Family membership: held values
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What usually comes next
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