Null Pointer Dereference in DrayTek VigorSwitch Models
CVE-2026-71920

6.9MEDIUM

Key Information:

Vendor

Draytek Corporation

Status
Vigorswitch G2540xs
Vigorswitch P2540xs
Vigorswitch Fx2120
Vigorswitch G2282x
Vendor
CVE Published:
24 August 2026

What is CVE-2026-71920?

Multiple models in the DrayTek VigorSwitch series have a vulnerability in the formlogout function that leads to a null pointer dereference. This issue arises from a lack of validation for an empty or missing Cookie header prior to string manipulation. If exploited, an attacker with valid administrative credentials can send a specially crafted request that results in the service crashing, leading to a denial of service. It is essential for administrators to ensure that necessary checks are in place to mitigate this vulnerability.

Affected Version(s)

VigorSwitch FX2120 0 < 3.9.10

VigorSwitch G1280 0 < 2.9.10

VigorSwitch G1282 0 < 2.9.10

References

https://www.draytek.com/about/security-advisory/multiple-...
vendor-advisory
https://www.vulncheck.com/advisories/draytek-vigorswitch-...
third-party-advisory

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Jincheng Wang (@winmt)
Le Yu (Nanjing University of Posts and Telecommunications)
Xiapu Luo (The Hong Kong Polytechnic University)
.