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Fencer Vulns
medium 4.9

CVE-2026-71920 json

DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogout

published 2026-08-24 2 mo ago modified 2026-10-13 26 d ago also EUVD-2026-64979

cvss
4.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • DrayTek Corporation VigorSwitch G2540xs 3.9.10
  • DrayTek Corporation VigorSwitch P2540xs 3.9.10
  • DrayTek Corporation VigorSwitch FX2120 3.9.10
  • DrayTek Corporation VigorSwitch G2282x 2.10.6
  • DrayTek Corporation VigorSwitch P2282x 2.10.6
  • DrayTek Corporation VigorSwitch Q2300x 2.10.7
  • DrayTek Corporation VigorSwitch PQ2300xb 2.10.7
  • DrayTek Corporation VigorSwitch G2542x 3.10.6
  • DrayTek Corporation VigorSwitch P2542x 3.10.6
  • DrayTek Corporation VigorSwitch P2542xh 3.10.6
  • DrayTek Corporation VigorSwitch PX2060 2.9.10
  • DrayTek Corporation VigorSwitch G1280 2.9.10
  • DrayTek Corporation VigorSwitch P1280 2.9.10
  • DrayTek Corporation VigorSwitch P1281x 2.9.10
  • DrayTek Corporation VigorSwitch G1282 2.9.10
  • DrayTek Corporation VigorSwitch P1282 2.9.10
  • DrayTek Corporation VigorSwitch G2121 2.9.10
  • DrayTek Corporation VigorSwitch P2121 2.9.10
  • DrayTek Corporation VigorSwitch PQ2121x 2.9.10
  • DrayTek Corporation VigorSwitch Q2121x 2.9.10
  • DrayTek Corporation VigorSwitch G2280x 2.9.10
  • DrayTek Corporation VigorSwitch P2280x 2.9.10
  • DrayTek Corporation VigorSwitch Q2200x 2.9.10
  • DrayTek Corporation VigorSwitch PQ2200xb 2.9.10
  • DrayTek Corporation VigorSwitch G2100 2.9.10
  • DrayTek Corporation VigorSwitch P2100 2.9.10
  • DrayTek Corporation VigorSwitch G2540x 2.9.10
  • DrayTek Corporation VigorSwitch P2540x 2.9.10

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.56% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 3.1 4.9 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 6.9 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/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:X/V:X/RE:X/U:X

Affected products

  • DrayTek Corporation VigorSwitch G2540xs
  • DrayTek Corporation VigorSwitch P2540xs
  • DrayTek Corporation VigorSwitch FX2120
  • DrayTek Corporation VigorSwitch G2282x
  • DrayTek Corporation VigorSwitch P2282x
  • DrayTek Corporation VigorSwitch Q2300x
  • DrayTek Corporation VigorSwitch PQ2300xb
  • DrayTek Corporation VigorSwitch G2542x
  • DrayTek Corporation VigorSwitch P2542x
  • DrayTek Corporation VigorSwitch P2542xh
  • DrayTek Corporation VigorSwitch PX2060
  • DrayTek Corporation VigorSwitch G1280
  • DrayTek Corporation VigorSwitch P1280
  • DrayTek Corporation VigorSwitch P1281x
  • DrayTek Corporation VigorSwitch G1282
  • DrayTek Corporation VigorSwitch P1282
  • DrayTek Corporation VigorSwitch G2121
  • DrayTek Corporation VigorSwitch P2121
  • DrayTek Corporation VigorSwitch PQ2121x
  • DrayTek Corporation VigorSwitch Q2121x
  • DrayTek Corporation VigorSwitch G2280x
  • DrayTek Corporation VigorSwitch P2280x
  • DrayTek Corporation VigorSwitch Q2200x
  • DrayTek Corporation VigorSwitch PQ2200xb
  • DrayTek Corporation VigorSwitch G2100
  • DrayTek Corporation VigorSwitch P2100
  • DrayTek Corporation VigorSwitch G2540x
  • DrayTek Corporation VigorSwitch P2540x

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.