CVE-2021-40856
Published: April 11, 2026
Official Description
Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
Risk Analysis
Auerswald COMfortel 1400 IP and 2600 IP devices are susceptible to an authentication bypass vulnerability. This flaw allows an attacker to bypass authentication mechanisms, potentially gaining unauthorized access to the device. Its inclusion in CISA's KEV catalog confirms active exploitation, making it a critical vulnerability.
This vulnerability is actively being exploited in the wild. The flaw is remotely exploitable, as it involves manipulating URL substrings.
Update Auerswald COMfortel 1400 IP and 2600 IP devices to firmware version 2.8G or later. Implement strong access controls and network segmentation for these devices.
Technical Analysis
CVE-2021-40856 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-40856 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Exploit & PoC Resources
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-40856 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1