CVE-2026-42790 | Vulnerability Intelligence

Stored catalog record

Source record retrieved 2026-10-28T10:25:18.069662+00:00. Scheduled imports handle updates; this page does not assert that the provider was queried just now.

Vulnerability overview

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g. permitted;DNS:allowed.example.com) to issue a leaf certificate that an OTP TLS client accepts as a valid identity for an out-of-scope hostname (e.g. victim.example.com): First, pubkey_cert:validate_names/6 in lib/public_key/src/pubkey_cert.erl only checks SAN DNS entries against nameConstraints. Per RFC 5280, a permitted DNS subtree only restricts certificates that contain a DNS-typed name. A leaf with no subjectAltName therefore trivially satisfies any permitted;DNS:... constraint regardless of its subject commonName. Second, public_key:pkix_verify_hostname/3 in lib/public_key/src/public_key.erl falls back to the subject commonName when no subjectAltName is present, extracting id-at-commonName attributes as presented IDs and matching them against the reference hostname. The strict pkix_verify_hostname_match_fun(https) matcher does not suppress this fallback. The result is that path validation accepts a CN-only leaf under a DNS-constrained intermediate (no SAN means the nameConstraints are not triggered), and hostname verification then accepts it via the CN fallback. The bypass is reachable from stock ssl:connect with verify_peer, a trusted CA, SNI, and the canonical strict https hostname matcher. This issue affects OTP from OTP 19.3 before OTP 29.0.1, OTP 28.5.0.1, OTP 27.3.4.12 and OTP 26.2.5.21, corresponding to public_key from 1.4 before 1.21.1, 1.20.3.1, 1.17.1.3 and 1.15.1.7.

Patch review priority

Assess exposure and vendor guidance

No higher-priority signal is available in the current stored evidence.

FIRST EPSS: 0.34% · percentile 27.9 · score date 2026-10-27.

EPSS estimates probability of exploitation in the next 30 days. It does not measure your exposure or prove exploitation. The elevated threshold is 10%; CISA KEV takes precedence. About FIRST EPSS ↗

Severity and scoring

CVSS score: 7.6 · HIGH
CVSS version: 4.0
CVSS vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/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
Weaknesses: CWE-295, CWE-297

CVSS measures technical severity; it does not establish whether this vulnerability is being exploited in your environment.

Known exploitation and remediation

Not listed in the CISA catalog retrieved for this record. This does not establish that exploitation has not occurred.

Verify affected versions and patch availability in the vendor advisory before making changes.

Affected products and versions

cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
From (inclusive): 19.3
Before (exclusive): 26.2.5.21
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
From (inclusive): 27.0
Before (exclusive): 27.3.4.12
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
From (inclusive): 28.0
Before (exclusive): 28.5.0.1
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
From (inclusive): 29.0
Before (exclusive): 29.0.1

These are NVD CPE applicability entries. Some products depend on configuration conditions; consult the official record to confirm applicability.

Advisories and references

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