PatchTheCVECVE-2021-27420: GE UR firmware versions prior to version 8.1x web server task does not properly handle receipt of unsupported
CVE-2021-27420 is a medium-severity flaw (CVSS 5.3) affecting multilin b30 firmware, multilin b90 firmware, multilin c60 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
GE UR firmware versions prior to version 8.1x web server task does not properly handle receipt of unsupported HTTP verbs, resulting in the web server becoming temporarily unresponsive after receiving a series of unsupported HTTP requests. When unresponsive, the web server is inaccessible. By itself, this is not particularly significant as the relay remains effective in all other functionality and communication channels.
Why this priority
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.1% (top 35%) |
| CISA exploited list | No |
| Weakness | CWE-20 |
| Published | 2022-03-23 |
| 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
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-2021-27420?
multilin b30 firmware: upgrade to 8.10; multilin b90 firmware: upgrade to 8.10; multilin c60 firmware: upgrade to 8.10. Exact commands for each OS are on this page.
Is CVE-2021-27420 being exploited?
CVE-2021-27420 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-2021-27420 affect?
CVE-2021-27420 affects multilin b30 firmware, multilin b90 firmware, multilin c60 firmware. Severity is medium (CVSS 5.3). GE UR firmware versions prior to version 8.1x web server task does not properly handle receipt of unsupported HTTP verbs, resulting in the web server becoming temporarily unresponsive after receiving a series of unsupported HTTP requests. W
How urgent is CVE-2021-27420?
Priority 40/100. Remotely exploitable, no login, no user action
Related CVEs
- CVE-2021-27428 CRITICAL 9.8 UPGRADE UPGRADE GE UR IED firmware versions prior to version 8.1x supports upgrading firmware using UR Setup configuration too
- CVE-2021-27426 CRITICAL 9.8 UPGRADE UPGRADE GE UR IED firmware versions prior to version 8.1x with “Basic” security variant does not allow the disabling o
- CVE-2021-27424 MEDIUM 5.3 UPGRADE UPGRADE GE UR firmware versions prior to version 8.1x shares MODBUS memory map as part of the communications guide
- CVE-2021-27422 HIGH 7.5 UPGRADE UPGRADE GE UR firmware versions prior to version 8.1x web server interface is supported on UR over HTTP protocol
- CVE-2021-27418 MEDIUM 5.3 UPGRADE UPGRADE GE UR firmware versions prior to version 8.1x supports web interface with read-only access