PatchTheCVECVE-2021-40856: Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ sub
CVE-2021-40856 is a high-severity flaw (CVSS 7.5) affecting comfortel 3600 ip firmware, comfortel 2600 ip firmware, comfortel 1400 ip firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
Why this priority
- High severity
- EPSS top 1%: very likely to be exploited
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 50.1% (top 1%) |
| CISA exploited list | No |
| Weakness | CWE-706 |
| Published | 2021-12-13 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Nuclei scan template: Auerswald COMfortel 1400/2600/3600 IP - Authentication Bypass
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-40856?
comfortel 3600 ip firmware: upgrade to newer than 2.8f; comfortel 2600 ip firmware: upgrade to newer than 2.8f; comfortel 1400 ip firmware: upgrade to newer than 2.8f. Exact commands for each OS are on this page.
Is CVE-2021-40856 being exploited?
CVE-2021-40856 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-40856 affect?
CVE-2021-40856 affects comfortel 3600 ip firmware, comfortel 2600 ip firmware, comfortel 1400 ip firmware. Severity is high (CVSS 7.5). Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
How urgent is CVE-2021-40856?
Priority 61/100. High severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action