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CVE-2026-82726
Published:August 31, 2026
Updated:September 24, 2026
Permissive Regular Expression vulnerability in ash-project ash_phoenix lets a remote client select the tenant an Ash application uses, or degrade the request, by sending a crafted Host header. AshPhoenix.Helpers.get_subdomain/2 stripped the root domain with String.replace(host, ~r/.?#{root_host}/, ""). The root host was interpolated raw, so each . became a wildcard and any metacharacter a pattern, and the replace was global and unanchored, so a match was removed from anywhere in the string. With root_host example.com, Host: foo.exampleXcom.attacker.net returned the tenant foo.attacker.net. A metacharacter-bearing or nil root host degraded the pattern or raised on every request. The comparison was also case-sensitive, so TENANT.EXAMPLE.COM and EXAMPLE.COM slipped past the root-host allowlist. conn.host comes from the client Host header. The fix matches the root host case-insensitively and only as an exact trailing suffix. This issue affects ash_phoenix: from 2.1.26 before 2.3.25.
Affected Packages
https://github.com/ash-project/ash_phoenix.git (GITHUB):
Affected version(s) >=v2.1.26 <v2.3.25
Fix Suggestion:
Update to version v2.3.25
ash_phoenix (HEX):
Affected version(s) >=2.1.26 <2.3.25
Fix Suggestion:
Update to version 2.3.25
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CVSS v4
Base Score:
6.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
LOW
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
LOW
Weakness Type (CWE)
Improper Handling of Case Sensitivity
Permissive Regular Expression
EPSS
Base Score:
0.30