CVE-2021-25811

Name: CVE-2021-25811
Creator: NVD / NIST
Published: 2021-04-29T16:15:09.847+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.63%

Last modified Jun 17, 2026

CVE-2021-25811 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. MERCUSYS Mercury X18G 1.0.5 devices allow Denial of service via a crafted value to the POST listen_http_lan parameter. Upon subsequent device restarts after this vulnerability is exploted the device will not be able to access the webserver unless the listen_http_lan parameter to uhttpd.json is manually fixed.. EPSS estimates a 1.63% chance of exploitation in the next 30 days.

Description

MERCUSYS Mercury X18G 1.0.5 devices allow Denial of service via a crafted value to the POST listen_http_lan parameter. Upon subsequent device restarts after this vulnerability is exploted the device will not be able to access the webserver unless the listen_http_lan parameter to uhttpd.json is manually fixed.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.63%

73.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mercusys	Mercury X18g Firmware	1.0.5

References

https://github.com/pokerfacett/MY_REQUEST/blob/master/Mercury%20Router%20X18g%20v1.0.5%20Denial%20of%20Service.mdBroken Link
https://www.mercurycom.com.cn/product-521-1.htmlProduct, Vendor Advisory
https://www.mercusys.com/en/Vendor Advisory
https://github.com/pokerfacett/MY_REQUEST/blob/master/Mercury%20Router%20X18g%20v1.0.5%20Denial%20of%20Service.mdBroken Link
https://www.mercurycom.com.cn/product-521-1.htmlProduct, Vendor Advisory
https://www.mercusys.com/en/Vendor Advisory

Timeline

Published: Apr 29, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-25811?

How severe is CVE-2021-25811?

CVE-2021-25811 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.63% probability of exploitation in the next 30 days.

How do I fix CVE-2021-25811?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-25811?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST