AUGUST 4, 2026
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Case File

CVE-2021-40523

HIGH · CVSS 7.5 EPSS 0.96% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2021-09-05 · Last synced 2026-08-04

CyberRota Analysis

AI analysis pending.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2021-40523
Severity
HIGH
CVSS
7.5
EPSS
0.96%

Original NVD Description

In Contiki 3.0, Telnet option negotiation is mishandled. During negotiation between a server and a client, the server may fail to give the WILL/WONT or DO/DONT response for DO and WILL commands because of improper handling of exception condition, which leads to property violations and denial of service. Specifically, a server sometimes sends no response, because a fixed buffer space is available for all responses and that space may have been exhausted.