CVE-2026-28808

Summary

Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias.

When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect.

This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl.

This issue affects OTP from OTP 17.0 before OTP 26.2.5.19, OTP 27.3.4.10, and OTP 28.4.2, corresponding to inets from 5.10 before 9.1.0.6, 9.3.2.4, and 9.6.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Affected Software

VendorProductVersion RangeStatus
ErlangOTP17.0 < *affected
ErlangOTP5.10 < *affected
ErlangOTP07b8f441ca711f9812fad9e9115bab3c3aa92f79 < *affected

Weaknesses

  • CWE-863: CWE-863 Incorrect Authorization

Workarounds

  • Move CGI scripts inside DocumentRoot and use alias instead of script_alias to ensure mod_auth resolves the correct path.
  • Apply URL-based access controls at a reverse proxy layer to block unauthenticated access to the script_alias URL prefix.
  • Remove mod_cgi from the httpd modules chain if CGI functionality is not required.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

erlang/otp: inets: Erlang OTP inets modules: Unauthenticated access to protected CGI scripts via incorrect authorization

Additional References

References