A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper escaping of shell meta-characters. This vulnerability allows an attacker to achieve remote command execution on the affected system. This issue primarily affects non-standard configurations where the "check password script" is used with %u and the samba-dcerpcd service is started as a system service.

A flaw was found in Samba’s certificate auto-enrollment Group Policy handling. When certificate auto-enrollment is enabled, Samba may retrieve a CA certificate over an unencrypted HTTP connection and install it into the local trust store without proper verification. An attacker with the ability to intercept or redirect network traffic could exploit this behavior to supply a malicious certificate authority certificate, potentially allowing interception or spoofing of trusted communications.

A flaw was found in Samba’s handling of NTFS-style reparse points on shares configured with read only = yes. Due to missing SMB-layer access checks, authenticated users with underlying filesystem write permissions may create or delete reparse point metadata through SMB operations even on read-only exports. This could allow modification of SMB-visible file behavior, including converting files into symbolic links or other reparse point types.

A flaw was found in Samba’s vfsworm module. The module is intended to provide write-once, read-many (WORM) protections by preventing modification of files after a configurable grace period. Due to insufficient validation during rename operations, an authenticated user with write access to a share could overwrite a protected file by renaming a newly created file over the existing WORM-protected file.

Samba: group policy certificate enrollment uses http:// without validation

Samba: Missing access check on reparse point operations

Samba file servers and classic (non-AD) domain controllers offer the SamValidatePasswordChange and SamValidatePasswordReset RPC services on the SAMR DCE/RPC service when running over NCACNIPTCP. Both services pass a username and password to the "check password script" that can be configured in smb.conf.

If the "check password script" is configured with the %u substitution character, the client-controlled username is passed to the "check password script" without escaping shell meta-characters, leading to a remote command execution vulnerability.

This is a non-standard configuration in several ways:

It affects Samba file servers and classic (non-AD) domain controllers that have the "check password script" configured with the %u substitution character. Active Directory Domain Controllers are not affected, they do not expand the username via the %u substitution character.

The problem is much less dangerous if %u has single quotes directly around it, e.g. '%u', but it's still possible to inject command line options.

Standard Samba file servers and classic domain controllers are also only affected if the samba-dcerpcd service is started as a system service, which can only happen if "rpc start on demand helpers" is set to the non-default setting "no". In the default configuration for DCE/RPC, smbd starts the samba-dcerpcd in a way that makes the vulnerable code inaccessible.

A flaw was found in Samba

A flaw was found in the Samba printing subsystem. Samba passes the client-controlled job description string to the command configured with the "print command" setting via the "%J" substitution character without escaping shell meta characters. A remote attacker could exploit this vulnerability by sending a specially crafted print job description that contains unescaped shell characters. This could lead to remote code execution on the affected system.

A flaw was found in Samba

A flaw was found in Samba's CTDB, the clustered database service used by Samba. Insufficient integrity validation of received CTDB protocol packets allows malformed packets containing invalid field lengths, improperly terminated strings, or inconsistent packet sizes to be processed without adequate bounds checking. A remote attacker with access to the CTDB private network may trigger a denial of service through process crashes or excessive memory consumption and, in limited cases, disclose adjacent memory contents.

A flaw was found in Samba. The smbd service daemon does not pick up group membership changes when re-authenticating an expired SMB session. This issue can expose file shares until clients disconnect and then connect again.

A flaw was found in Samba, in the front-end WINS hook handling: NetBIOS names from registration packets are passed to a shell without proper validation or escaping. Unsanitized NetBIOS name data from WINS registration packets are inserted into a shell command and executed by the Samba Active Directory Domain Controller’s wins hook, allowing an unauthenticated network attacker to achieve remote command execution as the Samba process.

All versions of Samba starting with 4.21.0 are vulnerable to a improper authorization issue. smbd does not pick up group membership changes when re-authenticating an expired SMB session.

Netlogon RPC Elevation of Privilege Vulnerability

Windows Kerberos RC4-HMAC Elevation of Privilege Vulnerability

Windows Kerberos Elevation of Privilege Vulnerability

A security feature bypass vulnerability exists in the way Key Distribution Center (KDC) determines if a service ticket can be used for delegation via Kerberos Constrained Delegation (KCD). To exploit the vulnerability, a compromised service that is configured to use KCD could tamper with a service ticket that is not valid for delegation to force the KDC to accept it.

A vulnerability has been found in Tenda AC18 15.03.05.19 and classified as problematic. This vulnerability affects unknown code of the file /etcro/smb.conf of the component Samba. The manipulation leads to weak password requirements. The attack can be initiated remotely. The complexity of an attack is rather high. The exploitation appears to be difficult. The exploit has been disclosed to the public and may be used.

A vulnerability was found in Samba's SMB2 packet signing mechanism. The SMB2 packet signing is not enforced if an admin configured "server signing = required" or for SMB2 connections to Domain Controllers where SMB2 packet signing is mandatory. This flaw allows an attacker to perform attacks, such as a man-in-the-middle attack, by intercepting the network traffic and modifying the SMB2 messages between client and server, affecting the integrity of the data.

A Type Confusion vulnerability was found in Samba's mdssvc RPC service for Spotlight. When parsing Spotlight mdssvc RPC packets, one encoded data structure is a key-value style dictionary where the keys are character strings, and the values can be any of the supported types in the mdssvc protocol. Due to a lack of type checking in callers of the dallocvalueforkey() function, which returns the object associated with a key, a caller may trigger a crash in tallocgetsize() when talloc detects that the passed-in pointer is not a valid talloc pointer. With an RPC worker process shared among multiple client connections, a malicious client or attacker can trigger a process crash in a shared RPC mdssvc worker process, affecting all other clients this worker serves.

An infinite loop vulnerability was found in Samba's mdssvc RPC service for Spotlight. When parsing Spotlight mdssvc RPC packets sent by the client, the core unmarshalling function slunpackloop() did not validate a field in the network packet that contains the count of elements in an array-like structure. By passing 0 as the count value, the attacked function will run in an endless loop consuming 100% CPU. This flaw allows an attacker to issue a malformed RPC request, triggering an infinite loop, resulting in a denial of service condition.

A path disclosure vulnerability was found in Samba. As part of the Spotlight protocol, Samba discloses the server-side absolute path of shares, files, and directories in the results for search queries. This flaw allows a malicious client or an attacker with a targeted RPC request to view the information that is part of the disclosed path.

A null pointer de-reference was found in the way samba kerberos server handled missing sname in TGS-REQ (Ticket Granting Server - Request). An authenticated user could use this flaw to crash the samba server.

An elevation of privilege vulnerability exists when an attacker establishes a vulnerable Netlogon secure channel connection to a domain controller, using the Netlogon Remote Protocol (MS-NRPC), aka 'Netlogon Elevation of Privilege Vulnerability'.

As per upstream samba advisory:

All versions of Samba from 3.5.0 onwards are vulnerable to a remote code execution vulnerability, allowing a malicious client to upload a shared library to a writable share, and then cause the server to load and execute it.

External References:

https://www.samba.org/samba/security/CVE-2017-7494.html

Acknowledgements:

Name: the Samba project Upstream: steelo

The ownerset function in smbcacls.c in smbcacls in Samba 4.0.x before 4.0.16 and 4.1.x before 4.1.6 removes an ACL during use of a --chown or --chgrp option, which allows remote attackers to bypass intended access restrictions in opportunistic circumstances by leveraging an unintended administrative change.

Samba 3.2.0 through 3.2.6, when registry shares are enabled, allows remote authenticated users to access the root filesystem via a crafted connection request that specifies a blank share name.

Stack-based buffer overflow in the replynttrans function in Samba 2.2.7a and earlier allows remote attackers to execute arbitrary code via a crafted request, a different vulnerability than CVE-2003-0201.

Buffer overflow in the calltrans2open function in trans2.c for Samba 2.2.x before 2.2.8a, 2.0.10 and earlier 2.0.x versions, and Samba-TNG before 0.3.2, allows remote attackers to execute arbitrary code.