{"id":"CVE-2026-42790","summary":"nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification","details":"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.\n\nTwo 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):\n\nFirst, 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.\n\nSecond, 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.\n\nThe 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.\n\nThis 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.","aliases":["EEF-CVE-2026-42790","GHSA-22cw-4ph4-6447"],"modified":"2026-08-21T18:27:47.072796439Z","published":"2026-05-27T15:09:01.860Z","related":["SUSE-SU-2026:22082-1","SUSE-SU-2026:3579-1","SUSE-SU-2026:3645-1","openSUSE-SU-2026:10947-1","openSUSE-SU-2026:11559-1","openSUSE-SU-2026:20907-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42790.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"1.4"},{"fixed":"*"},{"introduced":"19.3"},{"fixed":"*"},{"introduced":"b0c245e8132bb13171e277b1af59c0cec00c9459"},{"fixed":"*"}]}],"cna_assigner":"EEF","cwe_ids":["CWE-295","CWE-297"]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-42790.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-42790"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42790.json"},{"type":"WEB","url":"https://www.erlang.org/doc/system/versions.html#order-of-versions"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:39809"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:54757"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-42790"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42790.json"},{"type":"ADVISORY","url":"https://github.com/erlang/otp/security/advisories/GHSA-22cw-4ph4-6447"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42790"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2482286"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/0769050c69d73762672b0db1347b6993a5b31759"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/21abed64eb2026b5f82f432709e4e932f9be389a"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/fb67c6d1836f51105a96d8b769e71e4215a79457"},{"type":"PACKAGE","url":"https://github.com/erlang/otp"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/erlang/otp","events":[{"introduced":"a748cafdc7063d9f181ba12088db6458793ced2f"},{"fixed":"c9ce879f4ca194adc5393f52b2c4cd57b3c3d89d"},{"introduced":"601a012837ea0a5c8095bf24223132824177124d"},{"fixed":"a2394acad3e3b8fa74d40905cb79bac2ab68258a"},{"introduced":"9e6f6742c4d9e9915ee8af0dcb7d97cf1f836116"},{"fixed":"5770157eabdd4e8b0b83d64fd8b207c0150c2b64"},{"introduced":"550d7b7898706c7822362c42e7b93120c1d1f29a"},{"fixed":"f26c7e590c5d1b3afa0dee38093442df117822e3"},{"fixed":"0769050c69d73762672b0db1347b6993a5b31759"},{"fixed":"21abed64eb2026b5f82f432709e4e932f9be389a"},{"fixed":"fb67c6d1836f51105a96d8b769e71e4215a79457"}],"database_specific":{"cpe":"cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"19.3"},{"fixed":"26.2.5.21"},{"introduced":"27.0"},{"fixed":"27.3.4.12"},{"introduced":"28.0"},{"fixed":"28.5.0.1"},{"introduced":"29.0"},{"fixed":"29.0.1"}],"source":["CPE_RANGE","REFERENCES"]}}],"versions":["patch-base-27","OTP-27.3.4","OTP-29.0","patch-base-28","OTP-28.5","OTP-28.4","OTP-27.3.4.9","OTP-27.0","OTP-27.3.4.11","OTP-27.3.4.10","OTP-28.0","OTP-27.3.4.8","OTP-27.3.4.6","OTP-27.3.4.7","OTP-27.3","OTP-27.3.4.5","OTP-27.3.4.4","OTP-28.1","OTP-27.3.4.3","OTP-27.3.3","OTP-27.3.4.2","OTP-27.3.4.1","OTP-27.3.2","OTP-27.2","OTP-27.3.1","OTP-27.1"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-42790.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}