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Published: 5 May 2016

The canonicalize_username function in svnserve/cyrus_auth.c in Apache Subversion before 1.8.16 and 1.9.x before 1.9.4, when Cyrus SASL authentication is used, allows remote attackers to authenticate and bypass intended access restrictions via a realm string that is a prefix of an expected repository realm string.

From the Ubuntu Security Team

Daniel Shahaf and James McCoy discovered that Subversion did not properly verify realms when using Cyrus SASL authentication. A remote attacker could use this to possibly bypass intended access restrictions.



Cvss 3 Severity Score


Score breakdown


Package Release Status
Launchpad, Ubuntu, Debian
artful Not vulnerable
precise Ignored
(end of life)
Released (1.8.8-1ubuntu3.3)
Released (1.9.4-1)
wily Ignored
(end of life)
Released (1.9.3-2ubuntu1.1)
yakkety Not vulnerable
zesty Not vulnerable

Severity score breakdown

Parameter Value
Base score 6.8
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact None
Vector CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N