CVE-2026-103502

Improper Certificate Validation vulnerability in hexpm hex_core allows an attacker who can intercept HTTPS connections to impersonate hex.pm, repo.hex.pm or any other repository or API server to programs that use hex_core's default HTTP adapter on Erlang/OTP 24, or on OTP 25 when the operating system's CA certificates can't be loaded. hex_core:default_config/0 selects the built-in hex_http_httpc adapter. For an HTTPS request whose adapter config has no ssl option, hex_http_httpc:http_options/2 builds options that verify the server certificate against public_key:cacerts_get/0. When that call raises, the adapter prints a warning and sends the request without ssl options, so httpc uses the defaults of the ssl application, which before OTP 26 don't verify the server certificate. public_key:cacerts_get/0 doesn't exist on OTP 24, so every HTTPS request falls back there, and on OTP 25 it raises when no CA store is found. hex_core versions before 0.11.0 never set ssl options, so they don't verify the server certificate on OTP 25 and earlier whether or not a CA store is found. The fallback was intended and documented, but the documentation didn't make clear that it meant no certificate verification. Since hex_core 0.8.2 the README has warned that the built-in httpc adapter "has insecure default settings" and recommended other HTTP clients, and the adapter prints "using default ssl options which are insecure" on every request that falls back. hex_core 0.11.0 added certificate verification with the changelog entry "Use secure SSL defaults for OTP 25+". Neither the README nor the warning says that the server certificate isn't verified, the README doesn't say which OTP versions the warning applies to, and on OTP 25 without CA certificates the warning tells users to upgrade to OTP 25 or later, which they already run. This advisory is published so that users who took those notices as general advice know their HTTPS requests weren't authenticated. This issue affects hex_core: from 0.1.0 before 0.20.0.

• CWE-295
• CWE-636

• https://cna.erlef.org/cves/CVE-2026-103502.html
• https://github.com/hexpm/hex_core/commit/b7b3a42defb4ed8e20a5c68a4412ce68a95b7938
• https://github.com/hexpm/hex_core/commit/fbb6d9de472e5edb8d6fb6b32a91cb266137892e
• https://github.com/hexpm/hex_core/security/advisories/GHSA-p26c-h8c2-rwqj
• https://osv.dev/vulnerability/EEF-CVE-2026-103502

Published

Oct 12, 2026

Last Modified

Oct 13, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-103496In JetBrains YouTrack before 2026.2.19422 iDOR in inbox thre…5.4
• CVE-2026-103497In JetBrains YouTrack before 2026.2.19422 sSRF was possible …5.5
• CVE-2026-103499IBM WebSphere Application Server - Liberty 17.0.0.3 through …7.5
• CVE-2026-1035A flaw was found in the Keycloak server during refresh token…3.1
• CVE-2026-103500An attacker could cause a heap buffer overflow by getting a …
• CVE-2026-103501Heap buffer overflow in the HLL sketch deserialization of Ap…
• CVE-2026-103503Improper Certificate Validation vulnerability in hexpm hex a…5.9
• CVE-2026-103504Changing an organization team's permission through the API w…8.1
• CVE-2026-103505Improper neutralization of argument delimiters in the volume…6.5
• CVE-2026-103507Perforce P4 Search prior to 2026.4.2 does not restrict file …7.5
• CVE-2026-103510P4 Search prior to 2026.4.2 does not fail securely when its …9.5
• CVE-2026-103511Perforce P4 Search prior to 2026.4.2 does not validate file …5.1