cbcvebase.
CVE-2026-32746
published 2026-03-13

CVE-2026-32746: telnetd in GNU inetutils through 2.7 allows an out-of-bounds write in the LINEMODE SLC (Set Local Characters) suboption handler because add_slc does not check…

PriorityP275critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EXPLOIT
EPSS
23.67%
97.6th percentile
telnetd in GNU inetutils through 2.7 allows an out-of-bounds write in the LINEMODE SLC (Set Local Characters) suboption handler because add_slc does not check whether the buffer is full.

Affected

7 ranges
VendorProductVersion rangeFixed in
debianinetutils< inetutils 2:2.4-2+deb12u3 (bookworm)inetutils 2:2.4-2+deb12u3 (bookworm)
gnuinetutils<= 2.7
gnuinetutils>= 0 < 2:2.4-2+deb12u32:2.4-2+deb12u3
gnuinetutils>= 0 < 2:2.6-3+deb13u32:2.6-3+deb13u3
gnuinetutils>= 0 < 2:2.7-42:2.7-4
ubuntuinetutils
vllmvllm>= 0.15.1 < 0.17.00.17.0

Detection & IOCsextracted from sources · hover to see the quote

snort
alert telnet any any -> $HOME_NET any (msg:"ET EXPLOIT Telnet SLC Option Data Buffer Overflow Attempt (CVE-2026-32746)"; flow:established,to_server; content:"|ff fa 22|"; fast_pattern; content:"|ff f0|"; distance:109; reference:url,labs.watchtowr.com/a-32-year-old-bug-walks-into-a-telnet-server-gnu-inetutils-telnetd-cve-2026-32746/; reference:cve,2026-32746; classtype:web-application-attack; sid:2068415; rev:1; metadata:affected_product telnetd, attack_target Server, tls_state plaintext, created_at 2026_03_25, cve CVE_2026_32746, deployment Perimeter, deployment Internal, performance_impact Low, confidence Medium, signature_severity Major, tag Exploit, updated_at 2026_03_25, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application; target:dest_ip;)
bytes
|ff fa 22| ... |ff f0| (IAC SB LINEMODE ... IAC SE, distance:109)
  • The overflow occurs when more than ~34 SLC triplets are sent in a single LINEMODE SLC suboption. Each triplet is 3 bytes; the usable buffer is 104 bytes (108-byte slcbuf minus 4-byte header). Alert on LINEMODE SLC suboptions whose body exceeds 104 bytes (i.e., IAC SE appears more than 109 bytes after IAC SB LINEMODE).
  • SLC function codes greater than NSLC (18 / 0x12) in a LINEMODE suboption are the specific trigger for the vulnerable add_slc() code path. Inspect SLC triplet function bytes; values above 0x12 in a LINEMODE SB are anomalous and attack-indicative.
  • The Snort/Suricata ET rule (sid:2068415) detects the exploit by matching IAC SB LINEMODE (|ff fa 22|) followed by IAC SE (|ff f0|) at a distance of 109 bytes, which places the SE beyond the safe buffer boundary.
  • A public PoC and Docker lab environment exist (github.com/jeffaf/cve-2026-32746), and Wiz confirms a public exploit exists. Treat any telnetd ≤ 2.7 exposure as actively exploitable.
  • ·Debian 11 (bullseye) has no fix available as of the advisory date; only Debian 12/13/14 and sid have patches. Systems on bullseye remain vulnerable and cannot be patched via standard package update.
  • ·The ET Snort rule uses distance:109 (not within:), meaning it will match IAC SE anywhere beyond 109 bytes after IAC SB LINEMODE. Tune for your environment to reduce false positives on legitimate but large LINEMODE negotiations.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
osv9.8CRITICAL
vendor_debian9.8CRITICAL
vendor_ubuntu7.8HIGH
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