CVE-2021-40856
HighExploitedAuerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
Published Dec 13, 2021 · Updated Nov 21, 2024
Key Facts
Patch immediately- CVE-2021-40856 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting Comfortel 1400 Ip Firmware (Auerswald), Comfortel 2600 Ip Firmware (Auerswald), Comfortel 3600 Ip Firmware (Auerswald).
- It is exploited in the wild, listed in Industry KEV feed since Jun 7, 2025. No public exploit code is known.
- EPSS estimates a 50% probability of exploitation in the next 30 days.
- Fixed versions are available, including Comfortel 1400 Ip Firmware <=2.8f, Comfortel 2600 Ip Firmware <=2.8f, Comfortel 3600 Ip Firmware <=2.8f.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (30-day exploit likelihood)
50%
Higher than 98.8% of all scored CVEs
Exploited in the wild
Yes
1 catalog listing
Public exploit code
None known
Get the full CVE-2021-40856 brief as a PDF
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Description
Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Jun 7, 2025 | n/a | Not reported |
Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected Products
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Comfortel 1400 Ip FirmwareAuerswald | See advisory | 2.8f |
| Comfortel 2600 Ip FirmwareAuerswald | See advisory | 2.8f |
| Comfortel 3600 Ip FirmwareAuerswald | See advisory | 2.8f |
Patched Releases
Comfortel 1400 Ip Firmware
<=2.8f
Comfortel 2600 Ip Firmware
<=2.8f
Comfortel 3600 Ip Firmware
<=2.8f
Timeline
Publicly disclosed
Dec 13, 2021
Last updated
Nov 21, 2024
Added to Industry KEV feed
Jun 7, 2025
Weakness Type
- CWE-706 Use of Incorrectly-Resolved Name or Reference
References
- exploithttp://packetstormsecurity.com/files/165162/Auerswald-COMfortel-1400-2600-3600-IP-2.8F-Authentication-Bypass.html
- exploitVulnCheck exploitation report
- exploithttps://www.redteam-pentesting.de/en/advisories/-advisories-publicised-vulnerability-analyses
- exploithttps://www.redteam-pentesting.de/en/advisories/rt-sa-2021-004/-auerswald-comfortel-1400-2600-3600-ip-authentication-bypass
FAQ
Common Questions.
Auerswald COMfortel 1400 IP and 2600 IP before 2.8G devices allow Authentication Bypass via the /about/../ substring.
Affected: Comfortel 1400 Ip Firmware (Auerswald); Comfortel 2600 Ip Firmware (Auerswald); Comfortel 3600 Ip Firmware (Auerswald). The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Jun 7, 2025.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Comfortel 1400 Ip Firmware <=2.8f, Comfortel 2600 Ip Firmware <=2.8f, Comfortel 3600 Ip Firmware <=2.8f.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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