CVE-2026-71920

DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogout

MEDIUM

4.9

CVSS Score

Published: August 24, 2026 at 05:07 PM UTC

Updated: October 13, 2026 at 09:10 AM UTC

42 products affected across 1 vendorVigorswitch Q2200X FirmwareVigorswitch PQ2121X FirmwareVigorswitch PQ2200XB Firmware

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Severity

MEDIUM4.9

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Vigorswitch FX2120 Firmware · Draytek

95%

v < 3.9.10

Affected range stops below 3.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch G1282 Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch G2100 Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch G2121 Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch G2280X Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch G2540XS Firmware · Draytek

95%

v < 3.9.10

Affected range stops below 3.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch P1282 Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch P2100 Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch P2280X Firmware · Draytek

95%

v < 2.9.10

Affected range stops below 2.9.10, so it looks safe — our inference, not a vendor statement

Vigorswitch P2540XS Firmware · Draytek

95%

v < 3.9.10

Affected range stops below 3.9.10, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/

References (2)

Vendor Advisory

Source: cverecord

https://www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/

Third Party Advisory

Source: cverecord

https://www.vulncheck.com/advisories/draytek-vigorswitch-multiple-models-null-pointer-dereference-via-formlogout

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.9MEDIUMVulnCheck

Attack Vector: NETWORK
Complexity: LOW
Privileges: HIGH
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusDEFERRED

CWE

CWE-476

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