Vulnerability · Published Apr 15, 2026 · Assigned by GitHub_M
CVE-2026-40193Maddy Mail Server: LDAP Filter Injection via Unsanitized Username
High 8.2
In plain English
A high-severity security flaw in maddy from foxcpp. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | maddy | 0.9.3-r0 | ALPINE-CVE-2026-40193 |
| Alpine:v3.24 | maddy | 0.9.3-r0 | ALPINE-CVE-2026-40193 |
| Go | github.com/foxcpp/maddy | 0.9.3 | GHSA-5835-4gvc-32pc |
| Go | github.com/foxcpp/maddy | 0.9.3 | GO-2026-5137 |
Affected products (as reported)
Weakness: CWE-90 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
References
- https://github.com/foxcpp/maddy/security/advisories/GHSA-5835-4gvc-32pc x_refsource_CONFIRM
- https://github.com/foxcpp/maddy/commit/6a06337eb41fa87a35697366bcb71c3c962c44ba x_refsource_MISC
- https://github.com/foxcpp/maddy/releases/tag/v0.9.3 x_refsource_MISC