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6 <title>Samba - Security Announcement Archive</title>
11 <H2>CVE-2016-2114.html:</H2>
15 ==============================================================
16 == Subject: "server signing = mandatory" not enforced
18 == CVE ID#: CVE-2016-2114
20 == Versions: Samba 4.0.0 to 4.4.0
22 == Summary: Due to a bug Samba doesn't enforce required
23 == smb signing, even if explicitly configured. In
24 == addition the default for the active directory
25 == domain controller case was wrong.
27 ==============================================================
33 Due to a regression introduced in Samba 4.0.0,
34 an explicit "server signing = mandatory" in the [global] section
35 of the smb.conf was not enforced for clients using the SMB1 protocol.
37 As a result it does not enforce smb signing and allows man in the middle attacks.
39 This problem applies to all possible server roles:
40 standalone server, member server, classic primary domain controller,
41 classic backup domain controller and active directory domain controller.
43 In addition, when Samba is configured with "server role = active directory domain controller"
44 the effective default for the "server signing" option should be "mandatory".
46 During the early development of Samba 4 we had a new experimental
47 file server located under source4/smb_server. But before
48 the final 4.0.0 release we switched back to the file server
51 But the logic for the correct default of "server signing" was not
52 ported correctly ported.
54 Note that the default for server roles other than active directory domain
55 controller, is "off" because of performance reasons.
61 A patch addressing this defect has been posted to
63 https://www.samba.org/samba/security/
65 Additionally, Samba 4.4.2, 4.3.8 and 4.2.11 have been issued as
66 security releases to correct the defect. Samba vendors and administrators
67 running affected versions are advised to upgrade or apply the patch as
70 Note that Samba 4.4.1, 4.3.7 and 4.2.10 were privately released to vendors,
71 but had a regression, which is fixed in 4.4.2, 4.3.8 and 4.2.11.
77 An explicit "server signing = mandatory" in the [global]
78 together with "server min protocol = SMB2", should prevent
79 connections without signing protection. But that means
80 older clients without support for SMB2 (or higher) might
81 become unable to connect.
87 This vulnerability was discovered and researched by Stefan Metzmacher of
88 SerNet (https://samba.plus) and the Samba Team (https://www.samba.org).
89 He provides the fixes in collaboration with the Samba Team.