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CVE-2026-42790— nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification

Quick assessment

Affected
Erlang OTP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Erlang/OTP是Erlang/OTP开源的一个JavaScript编写的处理处理异常的库。该库可以捕捉node.js内置API引发的异常。 Erlang/OTP存在安全漏洞，该漏洞源于public_key模块中证书验证不当，允许通过主题通用名称回退绕过DNS名称约束，可能导致TLS主机名验证绕过。以下版本受到影响：OTP 19.3至26.2.5.21之前版本、27.3.4.12之前版本、28.5.0.1之前版本和29.0.1之前版本。

CVSS 7.6 · High EPSS 0.34% · P26

Affected Version Matrix 3

VendorProduct Version RangeStatus
Erlang OTP 1.4< * affected
19.3< * affected
b0c245e8132bb13171e277b1af59c0cec00c9459< * affected
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I. Basic Information for CVE-2026-42790

Vulnerability Information
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Vulnerability Title
nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Erlang/OTP 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Erlang/OTP是Erlang/OTP开源的一个JavaScript编写的处理处理异常的库。该库可以捕捉node.js内置API引发的异常。 Erlang/OTP存在安全漏洞，该漏洞源于public_key模块中证书验证不当，允许通过主题通用名称回退绕过DNS名称约束，可能导致TLS主机名验证绕过。以下版本受到影响：OTP 19.3至26.2.5.21之前版本、27.3.4.12之前版本、28.5.0.1之前版本和29.0.1之前版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Erlang OTP 1.4 ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Erlang OTP 19.3 ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-42790

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III. Intelligence Information for CVE-2026-42790

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Patches & Fixes for CVE-2026-42790 (3)

Vendor Advisories for CVE-2026-42790 (3)

Same Patch Batch · Erlang · 2026-05-27 · 3 CVEs total

CVE-2026-42789 7.0 HIGH Non-CA certificate accepted as intermediate issuer in public_key path validation
CVE-2026-42791 6.3 MEDIUM OCSP responder certificate validity period not checked in public_key

IV. Related Vulnerabilities

Same product: OTP
Same vendor: Erlang
Same weakness: CWE-295

V. Comments for CVE-2026-42790

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