CVE-2026-103502
hex_core's default HTTP adapter doesn't verify TLS certificates on OTP 24 and 25
Published Oct 12, 2026 · corrected/updated Oct 12, 2026 · evidence confidence high
## Summary 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. selects the built-in adapter. For an HTTPS request whose adapter config has no option, builds options that verify the server certificate against . When that call raises, the adapter prints a warning and sends the request without options, so httpc uses the defaults of the application, which before OTP 26 don't verify the server certificate. 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 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. ## Details 1. sets to . 2. and build their httpc options with . 3. For an URI whose adapter config has n
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-103502 is a unknown public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: hex_core (0.1.0 → 0.20.0). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: EPSS 0.2%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-295, CWE-636. Sources contributing to this record: cve_org, epss, github, osv. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Oct 12, 2026 · GitHub Advisory Database
Detected
## Summary 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. selects the built-in adapter. For an HTTPS request w
Oct 12, 2026 · GitHub Advisory Database
Fix available
hex_core fixed in 0.20.0
Oct 12, 2026 · GitHub Advisory Database
Fix available
hex_core fixed in 0.20.0
Oct 12, 2026 · GitHub Advisory Database
Updated
## Summary 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. selects the built-in adapter. For an HTTPS request w
Affected
- Hex hex_core0.1.0 → 0.20.0
Sources
- CVE.orgVulnerability recordCVE-2026-103502
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-103502
30-day exploitation probability 0.2%
first.org - GitHub Advisory DatabasePackage advisoryGHSA-p26c-h8c2-rwqj
GitHub Advisory Database record mirrored by OSV.
github.com - OSV.devPackage advisoryEEF-CVE-2026-103502
hex_core's default HTTP adapter doesn't verify TLS certificates on OTP 24 and 25
osv.dev