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Vulnerability · Published Sep 1, 2026 · Assigned by EEF

CVE-2026-73270httpd mod_auth directory protection bypassed by request path casing on case-insensitive filesystems

High 8.2

In plain English

A high-severity security flaw in OTP from Erlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 61% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.2High
Exploit odds (30 days)0.9%top 39.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Improper Handling of Case Sensitivity vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by requesting them with different casing, on deployments whose filesystem is case-insensitive. mod_auth:secret_path/3 decides whether a resolved filesystem path lies inside a protected directory block by running the configured directory path through re:run/3 without the caseless option. A request for /secret/file against a directory configured as /Secret therefore does not match, so the request is treated as unprotected and no authentication challenge is issued, while the filesystem resolves the differently cased path to the same file and mod_get serves it. Deployments on case-sensitive filesystems are unaffected, because there the filesystem itself rejects the mismatched casing. 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12erlangno fix listedDEBIAN-CVE-2026-73270
Debian:13erlang1:27.3.4.1+dfsg-1+deb13u4DEBIAN-CVE-2026-73270
Debian:14erlang1:29.0.6+dfsg-1DEBIAN-CVE-2026-73270
Ubuntu:22.04:LTSerlang1:24.2.1+dfsg-1ubuntu0.7UBUNTU-CVE-2026-73270
Ubuntu:22.04:LTSerlang1:24.2.1+dfsg-1ubuntu0.7USN-8827-1
Ubuntu:24.04:LTSerlang1:25.3.2.8+dfsg-1ubuntu4.7USN-8827-1
Ubuntu:24.04:LTSerlang1:25.3.2.8+dfsg-1ubuntu4.7UBUNTU-CVE-2026-73270
Ubuntu:26.04:LTSerlang1:27.3.4.6+dfsg-1ubuntu0.1USN-8827-1
Ubuntu:26.04:LTSerlang1:27.3.4.6+dfsg-1ubuntu0.1UBUNTU-CVE-2026-73270

Affected products (as reported)

VendorProductVersions
Erlang OTP 17.0 – before 27.3.4.1728.0 – before 28.5.0.629.0 – before 29.0.6
Erlang OTP 5.10 – before 9.3.2.79.4 – before 9.6.2.39.7 – before 9.7.2
Erlang OTP 84adefa331c4159d432d22840663c38f155cd4c1 – before *

Weakness: CWE-178 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References