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CVE-2013-4786 – High‑Severity IPMI 2.0 Authentication Flaw Exposes BMC Password Hashes

Key Takeaways

  • Severity: HIGH (CVSS 7.5)
  • Impact: Remote attackers can retrieve IPMI password hashes and crack them offline, compromising server BMCs.
  • Scope: Over 24 000 internet‑exposed servers (including Supermicro, Dell iDRAC, HPE iLO) still vulnerable.
  • Current threat: Active exploitation reported throughout 2026, with public tools harvesting hashes.
  • Action: Patch firmware, block BMC access from the internet, rotate passwords, and monitor for leaked hashes.

Overview

The Intelligent Platform Management Interface (IPMI) 2.0 specification defines the Remote Management Control Protocol (RMCP+) and the Authenticated Key‑Exchange Protocol (RAKP) used by Baseboard Management Controllers (BMCs). CVE-2013-4786 is an authentication flaw in the RAKP handshake that allows an unauthenticated remote attacker to capture the HMAC‑SHA1 value from the RAKP Message 2 response. This HMAC is effectively a password hash that can be cracked offline without further interaction with the target.

The vulnerability is pre‑authentication, meaning an attacker does not need valid credentials to obtain the hash. Once the hash is recovered, a dictionary or brute‑force attack can recover the clear‑text password, often the factory‑sticker password shipped by the hardware vendor.

Technical Details

  • Protocol flow: During IPMI 2.0 session establishment, the client sends RAKP Message 1 (username, random nonce). The BMC replies with RAKP Message 2, which includes an HMAC calculated over the username, nonces, and the shared password.
  • Flaw: The HMAC is sent unencrypted and without authentication. An attacker who can reach the BMC (typically on UDP 623) can capture this packet and extract the HMAC.
  • Offline cracking: The HMAC is essentially a PBKDF2‑like hash using HMAC‑SHA1. With a known username and captured nonces, an attacker can run a dictionary or GPU‑accelerated brute‑force attack against the hash. In practice, factory‑default passwords (e.g., “ADMIN”, “CALVIN”) are cracked in minutes.
  • Impact scope: Public scans in 2026 identified 36 872 exposed BMCs; of those, roughly 66 % leaked a hash. Researchers reported cracking ≈ 33 % of the captured hashes using common password lists.

Severity & Impact

MetricValue
CVSS v3.07.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
CWECWE‑255 (Credentials Management Errors)
ImpactConfidentiality breach (password hash exposure) – no direct integrity or availability impact, but credential compromise enables full BMC takeover.

The high CVSS score reflects the network‑accessible nature of the flaw, no authentication required, and the complete loss of confidentiality of BMC credentials.

Affected Products

The vulnerability affects any implementation of IPMI 2.0 that follows the RAKP specification, including:

  • BMC firmware from Supermicro, Dell iDRAC, HPE iLO, and Oracle (Fujitsu M10) platforms.
  • Generic Intel‑based IPMI controllers that expose the RMCP+ service on UDP 623.

Vendors have issued firmware updates for many of these products. For the complete list of affected vendors, products, and versions, see the official CVE page: https://vulnsocial.com/cve/CVE-2013-4786.

Actionable Insights – What to Do Now

  1. Identify exposed BMCs – Scan your network for open UDP 623 (or TCP 623 where applicable). Tools such as Nmap (nmap -sU -p 623 <target>) can flag reachable IPMI services.
  2. Check for leaked hashes – Use packet capture (e.g., tcpdump) to record RAKP exchanges and verify whether the HMAC is present. Public scripts exist to extract the hash from captured traffic.
  3. Prioritize high‑risk assets – Focus on internet‑facing BMCs (cloud‑hosted, colocation, remote sites). The recent threat‑intel shows that active exploitation is concentrated on publicly reachable interfaces.
  4. Correlate with threat feeds – Subscribe to VulnSocial’s CVE feed or monitor the live timeline at https://vulnsocial.com/cve/CVE-2013-4786 for spikes in exploitation attempts.
  5. Enforce strong passwords – Immediately replace factory defaults with complex, unique passwords. Consider integrating with a password manager or secret store.
  6. Network segmentation – Place BMCs on isolated management VLANs, restrict access to trusted IP ranges, and block inbound UDP 623 from the internet.
  7. Enable additional authentication – Where supported, enable certificate‑based authentication or two‑factor mechanisms for IPMI login.

Remediation & Mitigation

  1. Patch firmware – Apply the latest BMC firmware from the vendor. See the References section for vendor advisories.
  2. Disable remote IPMI access – If remote management is not required, turn off the IPMI service or block UDP 623 at the perimeter firewall.
  3. Rotate passwords – After patching, change the BMC password to a strong, random value. Document the new credentials securely.
  4. Implement network controls – Use ACLs, VLANs, or jump‑hosts to limit BMC access to authorized administrators only.
  5. Monitor for anomalous IPMI traffic – Deploy IDS/IPS signatures for RAKP messages and alert on unexpected sessions.
  6. Audit existing credentials – Verify that no default or weak passwords remain on any BMC, especially on devices that could not be patched immediately.

Bottom Line

CVE-2013-4786 remains a high‑severity risk more than a decade after its disclosure. With tens of thousands of BMCs still exposed and active exploitation observed in 2026, the threat is real and immediate. Patch, isolate, and rotate – those three steps are the fastest path to reducing risk.

References

For live threat intelligence, see the VulnSocial CVE page: https://vulnsocial.com/cve/CVE-2013-4786.

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