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Review reviewHigh

CVE-2026-42789

Erlang OTP, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1

Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP public_key (pubkey_cert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery. In lib/public_key/src/pubkey_cert.erl, pubkey_cert:validate_extensions/7 contains two flaws that together allow a certificate with basicConstraints cA:false and no keyUsage extension to be used as an intermediate issuer in a chain passed to public_key:pkix_path_validation/3: the cA:false clause recurses into the remaining extensions without rejecting the certificate when it i...

CVSS
7
EPSS
0.33%
25.5% percentile
CISA KEV
Not listed
Published
2026.05.27
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.33%
Technical severityCVSS 7

Vulnerability overview

Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP public_key (pubkey_cert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery. In lib/public_key/src/pubkey_cert.erl, pubkey_cert:validate_extensions/7 contains two flaws that together allow a certificate with basicConstraints cA:false and no keyUsage extension to be used as an intermediate issuer in a chain passed to public_key:pkix_path_validation/3: the cA:false clause recurses into the remaining extensions without rejecting the certificate when it i...

Affected product and versions

Product
Erlang OTP, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1
Affected versions
>= 0.22, >= 17.0, >= 84adefa331c4159d432d22840663c38f155cd4c1, >= 17.0 < 26.2.5.21, >= 27.0 < 27.3.4.12, >= 28.0 < 28.5.0.1, >= 29.0 < 29.0.1
Fixed versions
26.2.5.21, 27.3.4.12, 28.5.0.1, 29.0.1

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Erlang OTP, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CWE
CWE-295, CWE-296
CVE-2026-42789 — Erlang OTP, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1 | SECUFOCUS NOW