cbcvebase.
CVE-2001-0554
published 2001-08-14

CVE-2001-0554: Buffer overflow in BSD-based telnetd telnet daemon on various operating systems allows remote attackers to execute arbitrary commands via a set of options…

PriorityP270critical10CVSS 2.0
AVNACLAuNCCICAC
ITWEXPLOITVulnCheck KEV
Exploited in the wild
EPSS
37.90%
98.4th percentile
Buffer overflow in BSD-based telnetd telnet daemon on various operating systems allows remote attackers to execute arbitrary commands via a set of options including AYT (Are You There), which is not properly handled by the telrcv function.

Affected

84 ranges· showing 25
VendorProductVersion rangeFixed in
ciscocatos_telnet
debiandebian_linux
debiannetkit<= 0.17
debiannetkit-telnet< netkit-telnet 0.17-26 (bullseye)netkit-telnet 0.17-26 (bullseye)
debiannetkit-telnet-ssl< netkit-telnet 0.17-26 (bullseye)netkit-telnet 0.17-26 (bullseye)
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd
freebsdfreebsd

Detection & IOCsextracted from sources · hover to see the quote

  • The exploit triggers the vulnerability via the AYT (Are You There) telnet option combined with other telnet protocol options sent to port 23; detect anomalous sequences of IAC option negotiations (especially IAC WILL/DO with options 0x03, 0x18, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x27, 0x05) in a single session.
  • Monitor for a new listening port 7465 opened by in.telnetd process after exploitation; this is the backdoor bind shell spawned by the shellcode.
  • The exploit sets environment variables USER and TERM to 'zen-parse' during the NEW-ENVIRONMENT telnet sub-negotiation; alert on telnet NEW-ENVIRONMENT (option 39) submissions containing these values.
  • A worm is known to be actively exploiting this vulnerability in the wild; prioritize detection on internet-facing telnetd instances.
  • The overflow occurs in the telrcv() function during processing of heap-based telnet option responses; heap corruption artifacts (e.g., invalid free, corrupted malloc chunks) in telnetd crash logs are indicative of exploitation attempts.
  • On Cisco CatOS, exploitation causes the Telnet daemon to crash and results in a switch reload; unexpected switch reloads on Catalyst devices with telnet enabled should be investigated for this CVE.
  • ·The proof-of-concept exploit is tuned for RedHat 7.0 localhost and requires adjustment of --size and --name options for other targets; offsets are host-specific.
  • ·Exploitability depends on the hostname length returned by the AYT command (multiples of 3 letters affect the heap layout); brute-forcing may be required.
  • ·Many heap-using processes affect the required --size offset, making reliable exploitation environment-dependent.

CVSS provenance

nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
osv10.0CRITICAL
vulncheck10.0CRITICAL
vendor_debian10.0CRITICAL
vendor_redhat10.0CRITICAL
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