CVE-2025-14733: WatchGuard Firebox -- Out-of-Bounds Write RCE via IKEv2

Background

WatchGuard Firebox firewalls are widely deployed network security appliances used by SMBs and enterprises for perimeter protection, VPN, and threat detection. Fireware OS is the operating system running on these appliances, including the IKE daemon (iked) that handles IKEv2 VPN key exchange.

CVE-2025-14733 is an out-of-bounds write (CWE-787) in the Firebox iked process, exploitable without authentication against any Firebox configured with Mobile User VPN using IKEv2, or Branch Office VPN with IKEv2 and a dynamic gateway peer. Both configurations are common in enterprise deployments.

CISA added this to the KEV catalog on 2025-12-19. Unauthenticated RCE on a perimeter firewall is about as bad as it gets — the attacker controls the device enforcing security policy for everything behind it.

Technical Mechanism

CWE-787 (Out-of-Bounds Write) in the iked process occurs when processing IKEv2 negotiation packets. The IKEv2 protocol involves complex packet parsing during SA (Security Association) establishment, and a flaw in handling a specific IKEv2 payload causes a write beyond the bounds of an allocated buffer.

// Conceptual vulnerable pattern in IKEv2 packet parser
typedef struct {
    uint16_t payload_length;
    uint8_t  data[256];  // fixed-size buffer
} ike_payload_t;

void process_ike_payload(ike_payload_t *pkt, const uint8_t *input, uint16_t length) {
    // Bug: length comes from attacker-controlled packet field
    memcpy(pkt->data, input, length);  // OOB write if length > 256
}

By sending a specially crafted IKEv2 packet with a maliciously sized payload, an unauthenticated attacker can overwrite adjacent memory in the iked process, achieving controlled code execution. Since the IKE daemon processes packets before any authentication occurs, no credentials are needed.

Real-World Exploitation Evidence

CISA’s KEV listing confirms active exploitation. Unauthenticated RCE on perimeter firewalls gives an attacker total control over network policy enforcement. The WatchGuard SMB customer base is attractive to ransomware groups seeking network entry points. Post-exploitation of firewall appliances typically includes exfiltration of VPN credentials and certificate private keys, and installation of persistent backdoors that survive firewall policy changes.

Impact Assessment

• Unauthenticated remote code execution on the Firebox appliance
• Full compromise of network perimeter security appliance
• Access to VPN session credentials and private keys
• Ability to manipulate firewall policy, enabling further network access
• Persistent implant installation on the appliance
• Pivot to all networks served by the compromised firewall

Affected Versions

Remediation Steps

1. Apply WatchGuard’s Fireware OS update for CVE-2025-14733 immediately.
2. If patching is not immediately possible, disable IKEv2 for Mobile User VPN and Branch Office VPN.
3. Review firewall logs for anomalous IKEv2 negotiation attempts from unexpected sources.
4. Audit VPN credentials and rotate certificates if compromise is suspected.
5. Restrict IKEv2 traffic to known peer IP addresses via firewall ACLs where possible.
6. Enable WatchGuard’s intrusion prevention system (IPS) signatures for this CVE.

Detection Guidance

Log Sources: Firebox traffic monitor logs, IKEv2 negotiation logs, network flow data.

IOCs: Malformed or oversized IKEv2 packets from unknown sources; iked process crashes or restarts; unexpected admin-level processes spawned post-IKE negotiation.

Suricata rule:

alert udp $EXTERNAL_NET any -> $HOME_NET 500 (
  msg:"ET EXPLOIT WatchGuard Firebox IKEv2 OOB Write CVE-2025-14733";
  flow:to_server;
  content:"|00 20|"; offset:4; depth:2;  /* IKEv2 header marker */
  dsize:>512;
  threshold:type limit, track by_src, count 5, seconds 60;
  classtype:attempted-admin;
  sid:2099007; rev:1;
)

Timeline

References

• NVD — CVE-2025-14733
• CISA KEV — CVE-2025-14733
• MITRE CVE — CVE-2025-14733