CVE-2026-74994: inets, httpd: Authentication Bypass via Directory Namespace Collapse in httpd mod_auth

Severity: medium (CVSS 6.0 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-01 · updated 2026-09-08
Weakness: CWE-863

Description

The mod_auth module in OTP's inets httpd server, when configured with dets or mnesia authentication backends and multiple directory configuration blocks, collapses all directory blocks into a single shared user/group namespace. A user added to one protected directory is accepted as valid for all other protected directories on the same server instance. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Affected products

Erlang OTP: from 17.0 before 27.3.4.17; from 28.0 before 28.5.0.6; from 29.0 before 29.0.6; from 5.10 before 9.3.2.7; from 9.4 before 9.6.2.3; from 9.7 before 9.7.2 — fixed in 27.3.4.17, 28.5.0.6, 29.0.6, 9.3.2.7, 9.6.2.3, 9.7.2

How to fix

Upgrade to a fixed version: Erlang OTP 27.3.4.17, 28.5.0.6, 29.0.6, 9.3.2.7. Check the vendor advisory for mitigations.

References

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