← Vulnerability feed

Vulnerability record · CVE-2021-25811 · published 29 April 2021

CVE-2021-25811: Mercusys mercury x18g firmware vulnerability

Mercusys · Mercury X18g Firmware

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.

7.5 CVSS 3.1 High EPSS 1.6% · top 24.7%
7.5CVSS 3.1 base score, v2 7.8
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

Track CVE-2021-25811 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

6.1CVE-2021-25810Mercusys mercury x18g firmware cross-site scripting vulnerabilityCross site Scripting (XSS) vulnerability in MERCUSYS Mercury X18G 1.0.5 devices, via crafted values to the 'src_dport_start', 'src_dport_end', and 'd…EPSS 1.1%5.3CVE-2021-23241Mercusys mercury x18g firmware path traversal vulnerabilityMERCUSYS Mercury X18G 1.0.5 devices allow Directory Traversal via ../ in conjunction with a loginLess or login.htm URI (for authentication bypass) to…EPSS 13%5.3CVE-2021-23242Mercusys mercury x18g firmware path traversal vulnerabilityMERCUSYS Mercury X18G 1.0.5 devices allow Directory Traversal via ../ to the UPnP server, as demonstrated by the /../../conf/template/uhttpd.json URI.EPSS 1.8%

Source: NIST National Vulnerability Database (record CVE-2021-25811), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.