A vulnerability was found in Samba's "rpcecho" development server, a non-Windows RPC server used to test Samba's DCE/RPC stack elements. This vulnerability stems from an RPC function that can be blocked indefinitely. The issue arises because the "rpcecho" service operates with only one worker in the main RPC task, allowing calls to the "rpcecho" server to be blocked for a specified time, causing service disruptions. This disruption is triggered by a "sleep()" call in the "dcesrvechoTestSleep()" function under specific conditions. Authenticated users or attackers can exploit this vulnerability to make calls to the "rpcecho" server, requesting it to block for a specified duration, effectively disrupting most services and leading to a complete denial of service on the AD DC. The DoS affects all other services as "rpcecho" runs in the main RPC task.
A heap-based buffer overflow vulnerability was found in Samba within the GSSAPI unwrapdes() and unwrapdes3() routines of Heimdal. The DES and Triple-DES decryption routines in the Heimdal GSSAPI library allow a length-limited write buffer overflow on malloc() allocated memory when presented with a maliciously small packet. This flaw allows a remote user to send specially crafted malicious data to the application, possibly resulting in a denial of service (DoS) attack.
As per samba upstream advisory:
The Samba AD DC includes checks when adding service principals names (SPNs) to an account to ensure that SPNs do not alias with those already in the database. Some of these checks are able to be bypassed if an account modification re-adds an SPN that was previously present on that account, such as one added when a computer is joined to a domain.
An attacker who has the ability to write to an account can exploit this to perform a denial-of-service attack by adding an SPN that matches an existing service. Additionally, an attacker who can intercept traffic can impersonate existing services, resulting in a loss of confidentiality and integrity.
A design flaw was found in Samba's DirSync control implementation, which exposes passwords and secrets in Active Directory to privileged users and Read-Only Domain Controllers (RODCs). This flaw allows RODCs and users possessing the GETCHANGES right to access all attributes, including sensitive secrets and passwords. Even in a default setup, RODC DC accounts, which should only replicate some passwords, can gain access to all domain secrets, including the vital krbtgt, effectively eliminating the RODC / DC distinction. Furthermore, the vulnerability fails to account for error conditions (fail open), like out-of-memory situations, potentially granting access to secret attributes, even under low-privileged attacker influence.
As per samba upstream advisory:
On a Samba 4 AD DC the LDAP server in all versions of Samba from 4.0.0 onwards incorrectly validates permissions to modify passwords over LDAP allowing authenticated users to change any other users passwords, including administrative users.
All versions of Samba from 4.0.0 onwards are vulnerable to an information leak (compared with the established behaviour of Microsoft's Active Directory) when Samba is an Active Directory Domain Controller.
Missing access control checks on the LDAPSERVERSHOWDELETEDOID control in the DSDB database layer cause the LDAP server to disclose, to authenticated but not privileged users, the names and preserved attributes of deleted objects. (Microsoft AD simply does not return these objects on a search).
No information that was hidden before the deletion is visible, but in Microsoft Active Directory the whole object is also not visible without administrative rights, whereas Samba allows read of limited set of attributes that are preserved after delete.
Last updated 25 August 2025
The NTLMSSP authentication implementation in Samba 3.x and 4.x before 4.2.11, 4.3.x before 4.3.8, and 4.4.x before 4.4.2 allows man-in-the-middle attackers to perform protocol-downgrade attacks by modifying the client-server data stream to remove application-layer flags or encryption settings, as demonstrated by clearing the NTLMSSPNEGOTIATESEAL or NTLMSSPNEGOTIATESIGN option to disrupt LDAP security.
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.x before 3.6.23, 4.0.x before 4.0.16, and 4.1.x before 4.1.6 does not enforce the password-guessing protection mechanism for all interfaces, which makes it easier for remote attackers to obtain access via brute-force ChangePasswordUser2 (1) SAMR or (2) RAP attempts.
The internal DNS server in Samba 4.x before 4.0.18 does not check the QR field in the header section of an incoming DNS message before sending a response, which allows remote attackers to cause a denial of service (CPU and bandwidth consumption) via a forged response packet that triggers a communication loop, a related issue to CVE-1999-0103.
Samba 3.6.6 through 3.6.23, 4.0.x before 4.0.18, and 4.1.x before 4.1.8, when a certain vfs shadow copy configuration is enabled, does not properly initialize the SRVSNAPSHOTARRAY response field, which allows remote authenticated users to obtain potentially sensitive information from process memory via a (1) FSCTLGETSHADOWCOPYDATA or (2) FSCTLSRVENUMERATESNAPSHOTS request.
As per upstream samba advisory:
All versions of Samba from 3.5.0 to 4.2.0rc4 are vulnerable to an unexpected code execution vulnerability in the smbd file server daemon.
A malicious client could send packets that may set up the stack in such a way that the freeing of memory in a subsequent anonymous netlogon packet could allow execution of arbitrary code. This code would execute with root privileges.
Last updated 18 August 2025
All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegationnotallowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.
All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the (poorly named) dnsserver RPC pipe provides administrative facilities to modify DNS records and zones. Samba, when acting as an AD DC, stores DNS records in LDAP. In AD, the default permissions on the DNS partition allow creation of new records by authenticated users. This is used for example to allow machines to self-register in DNS. If a DNS record was created that case-insensitively matched the name of the zone, the ldbqsort() and dnsnamecompare() routines could be confused into reading memory prior to the list of DNS entries when responding to DnssrvEnumRecords() or DnssrvEnumRecords2() and so following invalid memory as a pointer.
Last updated 25 August 2025
A denial of service vulnerability was discovered in Samba's LDAP server before versions 4.7.12, 4.8.7, and 4.9.3. A CNAME loop could lead to infinite recursion in the server. An unprivileged local attacker could create such an entry, leading to denial of service.
An integer overflow flaw was found in the way samba read an EA list provided by the client. A malicious client could send a specially crafted EA list that wraps perfectly on a 32-bit boundary, causing the server to loop and re-process the list. This can cause Denial of Service via memory exhaustion.
Reference:
https://bugzilla.samba.org/showbug.cgi?id=10010 (curently private)
A flaw was found in the way Samba, as an Active Directory Domain Controller, implemented Kerberos name-based authentication. The Samba AD DC, could become confused about the user a ticket represents if it did not strictly require a Kerberos PAC and always use the SIDs found within. The result could include total domain compromise.
A flaw was found in all Samba versions before 4.10.17, before 4.11.11 and before 4.12.4 in the way it processed NetBios over TCP/IP. This flaw allows a remote attacker could to cause the Samba server to consume excessive CPU use, resulting in a denial of service. This highest threat from this vulnerability is to system availability.