CVE-2026-71920

DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogout

State: Published
Severity: 6.9 Medium
Published: Aug 24, 2026
Updated: Aug 24, 2026
Reserved: Aug 8, 2026

Description

Multiple DrayTek VigorSwitch models contain a null pointer dereference vulnerability in the formlogout function. The vulnerability is caused by missing checks for an empty or absent Cookie header before string handling. A remote attacker can trigger this vulnerability via a crafted request to crash the service and cause a denial of service. Exploitation requires valid administrative credentials for the device's web management interface.

Scores

CVSS	Score	Vector	Source
4.0	6.9 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N	VulnCheck
3.1	4.9 Medium	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H	VulnCheck

Weaknesses

CWE-476 NULL Pointer Dereference

Affected Products

Product	Versions
VigorSwitch G2540xsDrayTek Corporation	before 3.9.10Affected
VigorSwitch P2540xsDrayTek Corporation	before 3.9.10Affected
VigorSwitch FX2120DrayTek Corporation	before 3.9.10Affected
VigorSwitch G2282xDrayTek Corporation	before 2.10.6Affected
VigorSwitch P2282xDrayTek Corporation	before 2.10.6Affected
VigorSwitch Q2300xDrayTek Corporation	before 2.10.7Affected
VigorSwitch PQ2300xbDrayTek Corporation	before 2.10.7Affected
VigorSwitch G2542xDrayTek Corporation	before 3.10.6Affected
VigorSwitch P2542xDrayTek Corporation	before 3.10.6Affected
VigorSwitch P2542xhDrayTek Corporation	before 3.10.6Affected
VigorSwitch PX2060DrayTek Corporation	before 2.9.10Affected
VigorSwitch G1280DrayTek Corporation	before 2.9.10Affected
VigorSwitch P1280DrayTek Corporation	before 2.9.10Affected
VigorSwitch P1281xDrayTek Corporation	before 2.9.10Affected
VigorSwitch G1282DrayTek Corporation	before 2.9.10Affected
VigorSwitch P1282DrayTek Corporation	before 2.9.10Affected
VigorSwitch G2121DrayTek Corporation	before 2.9.10Affected
VigorSwitch P2121DrayTek Corporation	before 2.9.10Affected
VigorSwitch PQ2121xDrayTek Corporation	before 2.9.10Affected
VigorSwitch Q2121xDrayTek Corporation	before 2.9.10Affected
VigorSwitch G2280xDrayTek Corporation	before 2.9.10Affected
VigorSwitch P2280xDrayTek Corporation	before 2.9.10Affected
VigorSwitch Q2200xDrayTek Corporation	before 2.9.10Affected
VigorSwitch PQ2200xbDrayTek Corporation	before 2.9.10Affected
VigorSwitch G2100DrayTek Corporation	before 2.9.10Affected
VigorSwitch P2100DrayTek Corporation	before 2.9.10Affected
VigorSwitch G2540xDrayTek Corporation	before 2.9.10Affected
VigorSwitch P2540xDrayTek Corporation	before 2.9.10Affected

References

https://www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/vendor-advisory
VulnCheck Advisory: DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogoutthird-party-advisory

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