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Vulnerability record · CVE-2026-73673 · published 14 August 2026

CVE-2026-73673: Missing authentication for critical function vulnerability

Netis NC63 router firmware V3.0.0.3327 contains an unauthenticated firmware update vulnerability that allows unauthenticated attackers to submit unsigned firmware images by exploiting a missing authentication enforcement flaw in the Boa web server and netis.cgi CGI dispatcher. Attackers can send a multipart POST request to /cgi-bin/upload_fw.cgi without a valid session cookie, bypassing authentication because Boa grants access to any path containing '.cgi' regardless of cookie validation, and netis.cgi reads but does not enforce the authentication state before invoking the firmware update handler, which accepts images validated only by a forgeable additive checksum and static product strings rather than a cryptographic signature, potentially enabling persistent router compromise.

8.7 CVSS 4.0 High EPSS 0.54% · top 56.6% CWE-306 · Missing authentication for critical function Deferred
8.7CVSS 4.0 base score
0.54%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
24 Sep 2026Last modified by NVD

Description

Netis NC63 router firmware V3.0.0.3327 contains an unauthenticated firmware update vulnerability that allows unauthenticated attackers to submit unsigned firmware images by exploiting a missing authentication enforcement flaw in the Boa web server and netis.cgi CGI dispatcher. Attackers can send a multipart POST request to /cgi-bin/upload_fw.cgi without a valid session cookie, bypassing authentication because Boa grants access to any path containing '.cgi' regardless of cookie validation, and netis.cgi reads but does not enforce the authentication state before invoking the firmware update handler, which accepts images validated only by a forgeable additive checksum and static product strings rather than a cryptographic signature, potentially enabling persistent router compromise.

CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/ozcanpng/CVE-2026-73673
https://ozcanpng.dev/blog/cve-2026-73673-netis-nc63-unauthenticated-firmware-update/
https://www.netis-systems.com/products/NC63.html
https://www.netis-systems.com/support/downinfo.html?id=35
https://www.vulncheck.com/advisories/netis-nc63-unauthenticated-firmware-update-with-missing-cryptographic-firmware-auth

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Source: NIST National Vulnerability Database (record CVE-2026-73673), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.