CVE-2026-42769: Trust-Anchor Substitution via cert/issuer Typo in CMP rootCaKeyUpdate

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.5%

Up from 0.2% on 22 Oct 2026.

EPSS score, percentile 45.6 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

5.3 Medium

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (5)

Which versions are affected?

Affected

• from 4.0.0 to before 4.0.1
• from 3.6.0 to before 3.6.3
• from 3.5.0 to before 3.5.7
• from 3.4.0 to before 3.4.6

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

• 4.0.1 git commit (Patch)
• 3.6.3 git commit (Patch)
• 3.5.7 git commit (Patch)
• 3.4.6 git commit (Patch)
• OpenSSL Advisory (Vendor advisory)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

Issue Summary: An error in the callback used to verify the certificate provided in a Root CA key update Certificate Management Protocol (CMP) message response rendered the certificate validation ineffectual, which could lead to escalation of credentials from the Registration Authority (RA) level to the root Certification Authority (root CA) level. Impact Summary: The Registration Autority could…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-42769 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 9 Jun 2026.
• The CVE record carries a CVSS v3.1 base score of 5.3 (Medium), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.5% (percentile 45.6), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

Trust-Anchor Substitution via cert/issuer Typo in CMP rootCaKeyUpdate

Issue Summary: An error in the callback used to verify the certificate provided in a Root CA key update Certificate Management Protocol (CMP) message response rendered the certificate validation ineffectual, which could lead to escalation of credentials from the Registration Authority (RA) level to the root Certification Authority (root CA) level. Impact Summary: The Registration Autority could replace the root CA certificate for the CMP clients with an arbitrary root CA certificate. One of the parts of the Certificate Management Protocol (CMP), specified in RFC 9810, is Root Certification Authority (root CA) key Rollover, which is sent by the server in a message with type 'id-it-rootCaKeyUpdate'. As part of these messages, 'newWithOld' certificate, the new root CA certificate signed with the old root CA key, is provided, and verifying its signature is crucial for transferring the trust from the old CA key to the new one. The 'id-it-rootCaKeyUpdate' messages are expected to be processed with OSSL_CMP_get1_rootCaKeyUpdate(), that is expected to verify the 'newWithOld' certificate. A typo in the certificate chain building code led to adding an incorrect certificate ('newWithOld' instead of 'oldRoot') to the certificate chain, rendering the certificate verification process ineffectual (only the issuer name and the algorithm OIDs were verified by other parts of the verification code). An attacker who already has credentials that satisfy the CMP message protection checks can generate a new key pair and use a crafted self-signed certificate in its 'id-it-rootCaKeyUpdate' CMP messages which affected CMP clients would accept as a new trust anchor. Significant preconditions for the attack (having valid RA-level credentials) are the reason the issue was assigned Low severity. The FIPS modules are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline

Known exploited OpenSSL vulnerabilities

• CVE-2014-0160: OpenSSL Information Disclosure Vulnerability (added 4 May 2022)