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How the mentioned CVE works:
The vulnerability resides in the Server service (srvsvc) of Microsoft Windows, specifically within the NetPathCanonicalize RPC function. This function is used to canonicalize network paths (e.g., converting relative paths to absolute). A remote attacker sends a crafted RPC request over SMB (port 445/tcp or 139/tcp) containing an overly long path string. The service fails to properly validate the length of the path during canonicalization, copying user-supplied data into a fixed-size stack buffer without bounds checking. This stack-based buffer overflow overwrites the return address on the stack, allowing arbitrary code execution with SYSTEM privileges. The attack does not require authentication, making it wormable. Exploit code leverages named pipe transports (e.g., \PIPE\browser). The vulnerability was exploited in the wild by the Gimmiv.A worm in October 2008. Microsoft assigned MS08-067 to address it. The overflow is triggered during the “path canonicalization” process when processing malformed “NetPathCanonicalize” requests. Attackers can craft specific RPC opnum 0x1F (CanonicalizePathName) calls. The flaw affects both x86 and x64 systems. Disabling SMB or blocking RPC ports mitigates exposure.
dailycve form:
Platform: Multiple Windows versions
Version: Various service packs
Vulnerability : RPC buffer overflow
Severity: Critical
date: 2008-10-23
Prediction: Patched Oct 2008
Analytics under heading What Undercode Say:
Nmap scan for vulnerable systems nmap -p445 --script smb-vuln-ms08-067 <target> Metasploit detection msfconsole -q -x "use auxiliary/scanner/smb/smb_ms08_067; set RHOSTS <target>; run; exit" Bash check for patch (Windows registry via rpcclient) rpcclient -U "" -N <target> -c "srvinfo" | grep -i "OS Build" Python proof-of-concept snippet (non-destructive) import socket payload = b"\x00"1024 + b"\xcc"4 simple crash payload (full exploit omitted for safety)
How Exploit:
Exploitation uses a specially crafted SMB session to call the NetPathCanonicalize RPC function. Attackers send a malicious “path” parameter with directory traversal sequences (“\..\”) and a large number of backslashes to overflow the buffer. The overflow overwrites SEH (Structured Exception Handling) or direct return address, leading to shellcode execution. Public exploits target port 445, using Metasploit’s exploit/windows/smb/ms08_067_netapi. The worm Conficker later used a variant of this vulnerability.
Protection from this CVE:
- Apply Microsoft security bulletin MS08-067 immediately.
- Block TCP ports 139 and 445 at the firewall.
- Disable SMBv1 and the Server service on unaffected systems.
- Enable Windows Firewall and use host-based IPS rules.
- Isolate legacy systems that cannot be patched.
Impact:
- Remote unauthenticated code execution as SYSTEM.
- Wormable vulnerability (Conficker, Gimmiv.A spread massively).
- Full compromise of affected Windows hosts.
- Lateral movement within corporate networks.
- Data theft, backdoor installation, and botnet recruitment.
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Sources:
Reported By: www.cve.org
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