Authentication bypass in Samba

Published: 2017-07-12
Risk Low
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2017-11103
Exploitation vector Local network
Public exploit N/A
Vulnerable software
Server applications / Directory software, identity management

Vendor Samba

Security Bulletin

This security bulletin contains one low risk vulnerability.

1) Authentication bypass


Risk: Low

CVSSv3.1: 5.7 [CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-11103

CWE-ID: CWE-311 - Missing Encryption of Sensitive Data

Exploit availability: No


The vulnerability allows a remote attacker to impersonate a trusted server and intercept users' credentials.

The vulnerability exists due to the KDC-REP service name is stored in unencrypted "ticket" instead of encrypted "enc_part" and used later by the _krb5_extract_ticket() function. An attacker in local network can perform a man-in-the-middle attack, intercept the KDC-REP service name and impersonate a trusted server.

Successful exploitation of the vulnerability may allow an attacker to obtain credentials of all Samba users from Samba DRS replication service during password replication process between trusted and fake DC.


Update to version 4.6.6, 4.5.12 or 4.4.15

Vulnerable software versions

Samba: 4.0.0 - 4.6.5

External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.