CVE-2026-71938: DrayTek VigorSwitch buffer overflow in switch_lan_gvrp

CVE-2026-71938 · Severity: high · CVSS 7.2 · Published 2026-08-24

DrayTek VigorSwitch is a managed network switch used to connect and control network infrastructure in corporate environments. A buffer overflow vulnerability in the switch's web management interface allows an authenticated administrator to trigger a crash or potentially execute arbitrary code on the device, disrupting network connectivity and potentially compromising the integrity of the switch itself.

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

Quick answers

Is CVE-2026-71938 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-71938 being exploited in the wild.
How severe is CVE-2026-71938?
High severity, with a CVSS score of 7.2, published 24 August 2026.
Which products and versions are affected?
DrayTek VigorSwitch FX2120 before 3.9.10; DrayTek VigorSwitch G1280 before 2.9.10; DrayTek VigorSwitch G1282 before 2.9.10; DrayTek VigorSwitch G2100 before 2.9.10; and 24 more.
Is there a fix for CVE-2026-71938?
A patch was published on 2026-08-24: Firmware updates released for all affected models Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-71938 attacked?
It is attacked over the network.
Am I affected by CVE-2026-71938?
Check whether you run DrayTek VigorSwitch FX2120, DrayTek VigorSwitch G1280, DrayTek VigorSwitch G1282 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

This is a classic buffer overflow vulnerability (CWE-120) in the switch_lan_gvrp function caused by unsafe copying of the portList field into an undersized buffer without bounds checking. The vulnerability is reachable through the mainfunction.cgi web interface and requires valid administrative credentials and network access to the device's management interface. An authenticated attacker can supply crafted input via the portList parameter to overflow the buffer, causing a denial of service (crash) or potentially executing arbitrary commands with device privileges. Fixed firmware versions have been released for all affected VigorSwitch models as of August 2026.

Affected products

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

Timeline

  • 2026-08-24: disclosed
  • 2026-08-24: patched: Firmware updates released for all affected models

References

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