CVE-2026-28808: Erlang OTP incorrect authorization in inets mod_auth

CVE-2026-28808 · Severity: critical · CVSS 9.8 · Published 2026-04-07

A security flaw in the Erlang OTP web server library (inets) allows unauthorized users to bypass security rules intended to protect web scripts. This occurs when the server is configured to run scripts from a specific directory outside of the main web folder. An attacker could exploit this to run sensitive scripts or access restricted data without providing the required credentials.

Technologies: Erlang Inets, Erlang OTP. Vendors: Erlang.

Quick answers

Is CVE-2026-28808 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-28808 being exploited in the wild.
How severe is CVE-2026-28808?
Critical severity, with a CVSS score of 9.8, published 7 April 2026.
Which products and versions are affected?
Erlang Inets 5.10 to 9.6.2, 9.3.2.4, 9.1.0.6; Erlang OTP 17.0 to 28.4.2, 27.3.4.10, 26.2.5.19.
Is there a fix for CVE-2026-28808?
A patch was published on 2026-03-23: Initial fix commits authored Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-28808 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-28808?
Check whether you run Erlang Inets or Erlang OTP at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An incorrect authorization vulnerability exists in the Erlang OTP 'inets' HTTP server due to a path mismatch between 'mod_auth' and 'mod_cgi'. When 'script_alias' is used to map a URL prefix to a directory outside the 'DocumentRoot', 'mod_auth' incorrectly evaluates directory-based access controls against the 'DocumentRoot'-relative path instead of the actual resolved path. Meanwhile, 'mod_cgi' executes the script at the correctly resolved 'ScriptAlias' path. This allows a remote, unauthenticated attacker to bypass authentication requirements for CGI scripts. The issue is fixed in OTP versions 28.4.2, 27.3.4.10, and 26.2.5.19.

Affected products

  • Erlang OTP 17.0 to 28.4.2, 27.3.4.10, 26.2.5.19
  • Erlang inets 5.10 to 9.6.2, 9.3.2.4, 9.1.0.6

Timeline

  • 2026-03-23: patched: Initial fix commits authored
  • 2026-04-07: advisory: Vulnerability published by NVD and Erlang Ecosystem Foundation

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.