Intel

CVE-2008-4250

Microsoft Windows — Microsoft Windows Buffer Overflow Vulnerability

criticalKEV: actively exploitedPoCEPSS 99%

Description

The Server service in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP1 and SP2, Vista Gold and SP1, Server 2008, and 7 Pre-Beta allows remote attackers to execute arbitrary code via a crafted RPC request that triggers the overflow during path canonicalization, as exploited in the wild by Gimmiv.A in October 2008, aka "Server Service Vulnerability."

Source: CISA_KEVNVDCVELISTV5

Response & Mitigation

Why act now?

Prioritisation rationale

CVE-2008-4250 carries a CVSS score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) and sits at the 99.9th EPSS percentile, reflecting the fact that reliable, weaponised exploits — including the Metasploit module ms08_067_netapi — have been publicly available for over 15 years. Its addition to the CISA KEV list in May 2026 indicates that unpatched legacy Windows systems remain actively targeted in real-world attacks. For NIS2-obligated organisations operating Windows XP or Server 2003 assets in OT/ICS environments, medical networks, or industrial control systems — where patching cycles are often constrained — this vulnerability must be rated critical and addressed through immediate network isolation if patching is not feasible. Any system with TCP 445 reachable from an untrusted network and without KB958644 applied should be considered fully compromised until proven otherwise.

Runbook · Step 1

Immediate response (0-24 h)

  • Apply the patch: Microsoft Security Bulletin MS08-067 (KB958644) is the authoritative fix. Deploy it immediately to all affected systems — Windows 2000 SP4, XP SP2/SP3, Server 2003 SP1/SP2, Vista, and Server 2008.
  • Block SMB/RPC exposure: Close TCP 445 and 139, and UDP 137/138 at the perimeter firewall and between internal segments unless a documented business requirement exists. Any system reachable from the internet on these ports must be treated as a priority.
  • Isolate unpatched legacy systems: Move Windows 2000 and Server 2003 hosts that cannot be patched immediately into a quarantine VLAN with no routing to production networks.
  • Audit Server Service exposure: Confirm that the Windows Server Service (svchost.exe under netsvcs) is not unnecessarily exposed; disable it on hosts where it serves no operational purpose.
  • Forensic triage before patching: Any system that had TCP 445 reachable from untrusted networks should be treated as potentially compromised — capture a memory dump and preserve event logs before applying the patch.

Runbook · Step 2

Mitigation layers

  • Network segmentation: Enforce explicit deny rules for TCP 445/139 and UDP 137/138 on all internal firewalls and via GPO-based Windows Firewall policy. Permit SMB only over controlled, documented paths between designated file servers and clients.
  • Force Windows Firewall via GPO: Enable "Block all inbound connections" on legacy systems through Group Policy; document and minimise any exceptions.
  • Activate IPS signatures: Snort/Suricata signatures for MS08-067 have been available since 2008 — Snort SIDs 13892 and 13893 (and related SIDs in the exploit/windows ruleset). Ensure these run in blocking (IPS) mode, not detection-only.
  • Disable SMBv1: Set HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\SMB1 = 0 or run Set-SmbServerConfiguration -EnableSMB1Protocol $false on all systems that support it.
  • Least-privilege service accounts: Verify the Server Service does not run under a Domain Admin account — this limits lateral movement radius if exploitation occurs.
  • Authenticated vulnerability scan: Run Nessus (Plugin 34477) or equivalent against all Windows assets to confirm patch status and prioritise remediation queues.

Runbook · Step 3

Detection rules

  • Network telemetry (Zeek/Suricata): Alert on anomalous SMB connections to TCP 445 from external or unexpected internal sources, especially with oversized DCERPC payloads or connections to named pipes \PIPE\srvsvc or \PIPE\svcctl. Example: alert tcp any any -> $HOME_NET 445 (msg:"ET EXPLOIT MS08-067 Attempt"; content:"|ff|SMB"; sid:2008067;).
  • Windows Event Log: Event ID 7036 (service start/stop) for the Server Service in rapid succession may indicate a crash caused by a failed exploit attempt. Correlate with Event ID 4625 (logon failure) from the same source IP on port 445.
  • Sysmon EID 3 + EID 1 chain: Inbound connection to port 445 by svchost.exe (EID 3) followed by process creation with svchost.exe as parent and cmd.exe, powershell.exe, or wscript.exe as child (EID 1). KQL: SysmonEvent | where EventID == 1 and ParentImage endswith "svchost.exe" and Image endswith "cmd.exe".
  • EDR process ancestry: Flag any process tree where svchost.exe spawns an interactive shell or scripting engine — this is the canonical post-exploitation chain for RCE via the Server Service.
  • Zeek SMB logs: Filter smb_cmd events for command == "Trans2" with above-average payload length — a behavioural indicator of path canonicalization overflow attempts.

Metrics

Severity
critical
Priority score
229.60
KEV status
Actively exploited
Exploit maturity
actively exploited (KEV)
XIEM Effective CVSS
9.8
Source: nvd-v3
CVSS v3
9.8
CVSS v4
—
EPSS percentile
99.9 %
Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
EPSS score
98.8 %
High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
Published
2026-05-20 00:00 UTC
CWE
—

Affected operating systems

  • windows

    microsoft / windows_2000

  • windows

    microsoft / windows_server_2003

  • windows

    microsoft / windows_server_2008

  • windows

    microsoft / windows_vista

  • windows

    microsoft / windows_xp

Public exploit references

Public proof-of-concepts and detection templates for this vulnerability. Maturity ranges from reported PoCs through working detection scripts up to fully weaponized exploit modules. NEOSEC mirrors the code internally for forensic analysis; externally we only link to the original sources.

References & sources

IDCVE-2008-4250
Microsoft Windows — Microsoft Windows Buffer Overflow Vulnerability — CVE-2008-4250 | NEOSEC Intel