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maddy Mail Server LDAP Auth Module Interpolates Usernames into LDAP Filters Without Escaping, Allowing SMTP or IMAP Clients to Inject Arbitrary LDAP Expressions

Last refreshed2026-09-30

Status: UPDATED  |  Advisory ID: CVE-2026-40193

Key Details

CVECVE-2026-40193
CVSS Score / Version8.2 (High) / CVSS v3.1
Updated2026-06-17
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
CVSS Proseattack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is high; integrity impact is low; availability impact is none.
Affected productsmaddy_project maddy
Classified asCWE-90 (Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection'))

Affected Products, Subsystems & Sectors

VendorProductAffected VersionsPatch Status
maddy_projectmaddy
SubsystemsGeneral OT
SectorsMultiple

What to Know

maddy is a composable, all-in-one mail server. Versions prior to 0.9.3 contain an LDAP injection vulnerability in the auth.ldap module where user-supplied usernames are interpolated into LDAP search filters and DN strings via strings.ReplaceAll() without any LDAP filter escaping, despite the go-ldap/ldap/v3 library's ldap.EscapeFilter() function being available in the same import. This affects three code paths: the Lookup() filter, the AuthPlain() DN template, and the AuthPlain() filter. An attacker with network access to the SMTP submission or IMAP interface can inject arbitrary LDAP filter expressions through the username field in AUTH PLAIN or LOGIN commands. This enables identity spoofing by manipulating filter results to authenticate as another user, LDAP directory enumeration via wildcard filters, and blind extraction of LDAP attribute values using authentication responses as a boolean oracle or via timing side-channels between the two distinct failure paths. This issue has been fixed in version 0.9.3. (NVD)

What to Do

Monitor maddy_project's web page for any future patch releases. See vendor advisory link below.

References

SourceReference
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2026-40193
CVEhttps://www.cve.org/CVERecord?id=CVE-2026-40193
Vendor advisoryhttps://github.com/foxcpp/maddy/security/advisories/GHSA-5835-4gvc-32pc