CVE WatchAug 14, 2026

CVE-2026-42790

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints byp

CVSS

8.1

High

EPSS

0.3%

p27

KEV

—

Exploit Today

0-100

Published: May 27, 2026 · Last modified: Aug 14, 2026 · CWE-295 · CWE-297

EPSS · 30d

0.3%EPSS · 30 days0.3%

2026-08-182026-09-14

Technical 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.

Official references

Related CVEs

CVECVSSEPSSKEVRExploitTitleMod.

CVE-2026-52724—

—

———Kuma is a modern Envoy-based service mesh that can run on every cloud across both Kubernetes and VMs. Prior to 2.7.26, 2.9.16, 2.11.14, 2.12.11, and 2.13.7, Universal mode kuma-dp connections to an HTTPS control plane disable TLS peer verification when --ca-cert-file is not supplied and KUMA_CONTROL_PLANE_CA_CERT is unset. The dataplane authentication token is sent over the unverified connection, allowing an on-path attacker to intercept the token, impersonate the control plane, inject a forged bootstrap configuration, and take over the proxy. Standard Kubernetes installations created by kumactl install control-plane or the official Helm chart are unaffected because the mutating admission webhook injects KUMA_CONTROL_PLANE_CA_CERT into each sidecar. This issue is fixed in versions 2.7.26, 2.9.16, 2.11.14, 2.12.11, and 2.13.7.15h CVE-2026-50166—

—

———Kuma is a modern Envoy-based service mesh that can run on every cloud across both Kubernetes and VMs. Prior to 2.7.26, 2.9.16, 2.11.14, 2.12.11, and 2.13.7, a kumactl profile manually configured for an HTTPS control plane without --ca-cert-file disables TLS peer verification and sends API tokens over the unverified connection. An attacker on the network path can intercept user or administrator API tokens and act against the control plane as the compromised user. The default local profile is unaffected because it uses plain HTTP. This issue is fixed in versions 2.7.26, 2.9.16, 2.11.14, 2.12.11, and 2.13.7.16h CVE-2026-868894.8 MED

—

——0A certificate validation issue was addressed with improved certificate validation. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An attacker in a privileged network position may be able to intercept network traffic.6h CVE-2026-906233.7 LOW

18.3%

——6A weakness has been identified in andreashappe cochise up to 0.4.1. Affected is the function asyncssh.connect of the file src/cochise/ssh_connection.py of the component SSH Host Key Handler. Executing a manipulation can lead to improper certificate validation. The attack may be launched remotely. The attack requires a high level of complexity. The exploitability is told to be difficult. The exploit has been made available to the public and could be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.1d CVE-2026-906518.1 HIG

8.6%

——3Socket Firewall (socketdev/socket-registry-firewall) in registry mode before 2.0.0 does not verify upstream TLS certificates by default. When the api_ssl_verify and upstream_ssl_verify configuration keys are omitted from socket.yml, the generated configuration sets SOCKET_API_SSL_VERIFY='false' and UPSTREAM_SSL_VERIFY='false', and the OpenResty/Lua HTTP client used for outbound requests accepts any certificate, including self-signed and otherwise untrusted certificates, without validating the chain. An attacker positioned to intercept traffic between Socket Firewall and the Socket API or an upstream package registry can present a crafted certificate and modify responses in transit, including substituting malicious package content or altering the allow/block decisions the firewall enforces. Setting api_ssl_verify: true and upstream_ssl_verify: true enables verification; however, in versions before 1.1.334, the generated nginx configuration did not emit lua_ssl_trusted_certificate, and thus verification could not be used successfully without manually patching the generated configuration. Version 2.0.0 changes the default for both settings to true.2d CVE-2026-906477.4 HIG

3.4%

——1ASE/Kalkitech ASE2000 V2 Communication Test Set 2.35 through 2.37 on Windows contains an improper certificate validation vulnerability in the IEC 60870-5-104 TLS client (Task Mode). This allows a network-positioned attacker to bypass certificate validation via a certificate with multiple simultaneous faults, enabling a Man-in-the-Middle attack on protected communications.13h