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CVE-2026-103502VulnerabilityPublished Updated

Rebar3: Improper Certificate Validation vulnerability

Affects rebar3Source GCVE Database

0
Authoritative record:CVE-2026-103502· Medium 5.9

Not known to be exploited · CVSS 5.9 Medium.

Data as of 28 Oct 2026, 22:31 UTC

CVSS 4.0 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10erlang-hexpkg:deb/ubuntu/erlang-hex?arch=source&distro=stonkingOther threatsAffected
  • =2.0.6-2build1
  • =2.5.1-2
Fixed in–
Ubuntu 26.10rebar3pkg:deb/ubuntu/rebar3?arch=source&distro=stonkingOther threatsAffected
  • 3.26.0-1 – 3.27.0-6
4 affected builds
Fixed in–
Ubuntu 26.04 LTSerlang-hexpkg:deb/ubuntu/erlang-hex?arch=source&distro=resoluteOther threatsAffected
  • =2.0.6-2
  • =2.0.6-2build1
Fixed in–
Ubuntu 26.04 LTSrebar3pkg:deb/ubuntu/rebar3?arch=source&distro=resoluteOther threatsAffected
  • =3.24.0-1
  • =3.25.1-1
  • =3.26.0-1
Fixed in–
Ubuntu 24.04 LTSerlang-hexpkg:deb/ubuntu/erlang-hex?arch=source&distro=nobleOther threatsAffected
  • =2.0.5-1
Fixed in–
Ubuntu 24.04 LTSrebar3pkg:deb/ubuntu/rebar3?arch=source&distro=nobleOther threatsAffected
  • =3.19.0-1
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

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.

References

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