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CVE-2026-71920— DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogout

Quick assessment

Affected
DrayTek Corporation VigorSwitch G2540xs
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

多款 DrayTek VigorSwitch 设备在 formlogout 函数中存在空指针解引用漏洞。该漏洞的成因是在进行字符串处理之前，未对缺失或为空的 Cookie 头部字段进行充分检查。远程攻击者可通过发送精心构造的请求来触发此漏洞，从而导致服务崩溃并引发拒绝服务（DoS）攻击。然而，利用此漏洞需要攻击者具备该设备 Web 管理界面的有效管理员凭据。

CVSS 4.9 · Medium EPSS 0.39% · P32

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 28

VendorProduct Version RangeStatus
DrayTek Corporation VigorSwitch FX2120 < 3.9.10 affected
DrayTek Corporation VigorSwitch G1280 < 2.9.10 affected
DrayTek Corporation VigorSwitch G1282 < 2.9.10 affected
DrayTek Corporation VigorSwitch G2100 < 2.9.10 affected
DrayTek Corporation VigorSwitch G2121 < 2.9.10 affected
DrayTek Corporation VigorSwitch G2280x < 2.9.10 affected
DrayTek Corporation VigorSwitch G2282x < 2.10.6 affected
DrayTek Corporation VigorSwitch G2540x < 2.9.10 affected
DrayTek Corporation VigorSwitch G2540xs < 3.9.10 affected
DrayTek Corporation VigorSwitch G2542x < 3.10.6 affected
DrayTek Corporation VigorSwitch P1280 < 2.9.10 affected
DrayTek Corporation VigorSwitch P1281x < 2.9.10 affected
DrayTek Corporation VigorSwitch P1282 < 2.9.10 affected
DrayTek Corporation VigorSwitch P2100 < 2.9.10 affected
DrayTek Corporation VigorSwitch P2121 < 2.9.10 affected
DrayTek Corporation VigorSwitch P2280x < 2.9.10 affected
DrayTek Corporation VigorSwitch P2282x < 2.10.6 affected
DrayTek Corporation VigorSwitch P2540x < 2.9.10 affected
DrayTek Corporation VigorSwitch P2540xs < 3.9.10 affected
DrayTek Corporation VigorSwitch P2542x < 3.10.6 affected
DrayTek Corporation VigorSwitch P2542xh < 3.10.6 affected
DrayTek Corporation VigorSwitch PQ2121x < 2.9.10 affected
DrayTek Corporation VigorSwitch PQ2200xb < 2.9.10 affected
DrayTek Corporation VigorSwitch PQ2300xb < 2.10.7 affected
DrayTek Corporation VigorSwitch PX2060 < 2.9.10 affected
DrayTek Corporation VigorSwitch Q2121x < 2.9.10 affected
DrayTek Corporation VigorSwitch Q2200x < 2.9.10 affected
DrayTek Corporation VigorSwitch Q2300x < 2.10.7 affected
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I. Basic Information for CVE-2026-71920

Vulnerability Information
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Vulnerability Title
DrayTek VigorSwitch Multiple Models NULL Pointer Dereference via formlogout
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
空指针解引用
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
DrayTek Corporation VigorSwitch G2540xs 0 ~ 3.9.10 -
DrayTek Corporation VigorSwitch P2540xs 0 ~ 3.9.10 -
DrayTek Corporation VigorSwitch FX2120 0 ~ 3.9.10 -
DrayTek Corporation VigorSwitch G2282x 0 ~ 2.10.6 -
DrayTek Corporation VigorSwitch P2282x 0 ~ 2.10.6 -
DrayTek Corporation VigorSwitch Q2300x 0 ~ 2.10.7 -
DrayTek Corporation VigorSwitch PQ2300xb 0 ~ 2.10.7 -
DrayTek Corporation VigorSwitch G2542x 0 ~ 3.10.6 -
DrayTek Corporation VigorSwitch P2542x 0 ~ 3.10.6 -
DrayTek Corporation VigorSwitch P2542xh 0 ~ 3.10.6 -
DrayTek Corporation VigorSwitch PX2060 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G1280 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P1280 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P1281x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G1282 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P1282 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G2121 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P2121 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch PQ2121x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch Q2121x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G2280x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P2280x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch Q2200x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch PQ2200xb 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G2100 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P2100 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch G2540x 0 ~ 2.9.10 -
DrayTek Corporation VigorSwitch P2540x 0 ~ 2.9.10 -

II. Public POCs for CVE-2026-71920

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-71920

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Vendor Advisories for CVE-2026-71920 (2)

Same Patch Batch · DrayTek Corporation · 2026-08-24 · 40 CVEs total

CVE-2026-71914 9.8 CRITICAL DrayTek VigorAP Multiple Models Pre-Authentication OS Command Injection via dray_apm
CVE-2026-71921 9.8 CRITICAL DrayTek VigorSwitch Multiple Models Pre-Authentication OS Command Injection via setget.cgi
CVE-2026-71933 9.1 CRITICAL DrayTek VigorSwitch Multiple Models Missing Authorization in Syslog Functions
CVE-2026-71922 7.5 HIGH DrayTek VigorSwitch Multiple Models Pre-Authentication NULL Pointer Dereference via setget
CVE-2026-71934 7.2 HIGH DrayTek VigorSwitch Multiple Models Buffer Overflow via pingtrace
CVE-2026-71905 7.2 HIGH DrayTek VigorAP Multiple Models OS Command Injection via ExportSettings
CVE-2026-71919 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via sysreboot
CVE-2026-71910 7.2 HIGH DrayTek VigorAP Multiple Models OS Command Injection via apautotest
CVE-2026-71906 7.2 HIGH DrayTek VigorAP Multiple Models OS Command Injection via setLan
CVE-2026-71912 7.2 HIGH DrayTek VigorAP Multiple Models Buffer Overflow via apautotest
CVE-2026-71917 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via pingtrace
CVE-2026-71907 7.2 HIGH DrayTek VigorAP Multiple Models OS Command Injection via setcamset
CVE-2026-71925 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via getDetail
CVE-2026-71915 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via jsonstatus
CVE-2026-71923 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via auth_set
CVE-2026-71935 7.2 HIGH DrayTek VigorSwitch Multiple Models Buffer Overflow via webBackupAction
CVE-2026-71941 7.2 HIGH DrayTek VigorSwitch Multiple Models Buffer Overflow via diag_logmail
CVE-2026-71938 7.2 HIGH DrayTek VigorSwitch Multiple Models Buffer Overflow via switch_lan_gvrp
CVE-2026-71939 7.2 HIGH DrayTek VigorSwitch Multiple Models Buffer Overflow via acl_general_setup Add ACE
CVE-2026-71918 7.2 HIGH DrayTek VigorSwitch Multiple Models OS Command Injection via webBackupAction

Showing top 20 of 40 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: VigorSwitch G2540xs
Same vendor: DrayTek Corporation
Same weakness: CWE-476

V. Comments for CVE-2026-71920

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