cbcvebase.
CVE-2018-6000
published 2018-01-22

CVE-2018-6000: An issue was discovered in AsusWRT before 3.0.0.4.384_10007. The do_vpnupload_post function in router/httpd/web.c in vpnupload.cgi provides functionality for…

PriorityP188critical9.8CVSS 3.0
AVNACLPRNUINSUCHIHAH
ITWEXPLOITVulnCheck KEV
Exploited in the wild
EPSS
84.20%
99.7th percentile
An issue was discovered in AsusWRT before 3.0.0.4.384_10007. The do_vpnupload_post function in router/httpd/web.c in vpnupload.cgi provides functionality for setting NVRAM configuration values, which allows attackers to set the admin password and launch an SSH daemon (or enable infosvr command mode), and consequently obtain remote administrative access, via a crafted request. This is available to unauthenticated attackers in conjunction with CVE-2018-5999.

Affected

1 ranges
VendorProductVersion rangeFixed in
asusasuswrt< 3.0.0.4.384_100073.0.0.4.384_10007

Detection & IOCsextracted from sources · hover to see the quote

url/vpnupload.cgi
portUDP/9999
command/usr/sbin/telnetd -l /bin/sh -p #{telnet_port}
otherateCommand_flag=1
pathrouter/httpd/web.c
bytes
0x0c 0x15 0x33 0x00
  • Detect unauthenticated HTTP POST requests to /vpnupload.cgi containing the multipart form field 'ateCommand_flag' set to '1', which enables PKT_SYSCMD mode on the router.
  • Monitor for UDP packets to port 9999 (infosvr) with the header byte sequence 0x0C 0x15 0x33 0x00 (NET_SERVICE_ID_IBOX_INFO / NET_PACKET_TYPE_CMD / NET_CMD_ID_MANU_CMD), indicating an attempt to send a PKT_SYSCMD command.
  • Alert on inbound UDP 512-byte packets to port 9999 on AsusWRT devices containing a shell command string such as '/usr/sbin/telnetd -l /bin/sh', indicating active exploitation for remote shell spawning.
  • Detect the authentication bypass condition: unauthenticated POST requests reaching handler->input() in the AsusWRT HTTP server, which should normally require auth_result == 0.
  • After exploitation, watch for new unexpected TCP listening ports (random high ports) on AsusWRT devices, as the exploit starts telnetd on a random port above 1024.
  • ·The exploit chain requires CVE-2018-5999 (auth bypass) to be present alongside CVE-2018-6000; CVE-2018-6000 alone is not directly exploitable by an unauthenticated attacker without the auth bypass.
  • ·The exploit was confirmed on AsusWRT v3.0.0.4.380.7743 (RT-AC68U) and may affect all versions prior to v3.0.0.4.384.10007; detections should be scoped to these firmware versions.
  • ·The attack vector is LAN-only (local network); the infosvr UDP service on port 9999 and the HTTP server are not expected to be reachable from the WAN in default configurations.
  • ·CVE-2018-6000 can also be abused to overwrite the web interface admin password and enable SSH, providing an alternative RCE path beyond the infosvr PKT_SYSCMD method.

CVSS provenance

nvdv3.09.8CRITICALCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
vulncheck9.8CRITICAL
vendor_cisco8.6HIGH
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