What is CVE-2026-71936?

CVE-2026-71936 is DrayTek VigorSwitch Multiple Models Buffer Overflow via sysreboot. The supplied enrichment data classifies it as Memory Corruption mapped to CWE-120 Classic Buffer Overflow.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-71936. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-71936 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-71936. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-71936 using CVSS 7.2, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

highMemory Corruption

CVE-2026-71936

CVE-2026-71936 — DrayTek VigorSwitch Multiple Models Buffer Overflow via sysreboot

Multiple DrayTek VigorSwitch models contain a buffer overflow vulnerability in the sysreboot function. The vulnerability is caused by unsafe concatenation of split valueN data into a fixed-size buffer. A remote attacker can trigger this vulnerability via crafted input, causing a denial of service or potentially executing arbitrary commands. Exploitation requires valid administrative credentials for the device's web management interface.

Published Aug 24, 2026Updated Aug 24, 2026Sources: NVD, DrayTek Corporation (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

ahead of 0% of scored CVEs

Affects

DrayTek Corporation

28 products listed

CVSS base

7.2

high · 2 sources

Remediation

The vendor's own words where we have them.

Upgrade VigorSwitch G2540xs to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
DrayTek Corporation	VigorSwitch G2540xs	0 to < 3.9.10	Vulnerable
DrayTek Corporation	VigorSwitch P2540xs	0 to < 3.9.10	Vulnerable
DrayTek Corporation	VigorSwitch FX2120	0 to < 3.9.10	Vulnerable
DrayTek Corporation	VigorSwitch G2282x	0 to < 2.10.6	Vulnerable
DrayTek Corporation	VigorSwitch P2282x	0 to < 2.10.6	Vulnerable
DrayTek Corporation	VigorSwitch Q2300x	0 to < 2.10.7	Vulnerable
DrayTek Corporation	VigorSwitch PQ2300xb	0 to < 2.10.7	Vulnerable
DrayTek Corporation	VigorSwitch G2542x	0 to < 3.10.6	Vulnerable
DrayTek Corporation	VigorSwitch P2542x	0 to < 3.10.6	Vulnerable
DrayTek Corporation	VigorSwitch P2542xh	0 to < 3.10.6	Vulnerable
DrayTek Corporation	VigorSwitch PX2060	0 to < 2.9.10	Vulnerable
DrayTek Corporation	VigorSwitch G1280	0 to < 2.9.10	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

High

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
7.2	CVSS 3.1	high	1.2	5.9	NVD, DrayTek Corporation (CNA), GHSA
8.6	CVSS 4.0	high	—	—	DrayTek Corporation (CNA)

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Modify Memory
Execute Unauthorized Code or Commands
DoS: Crash, Exit, or Restart
DoS: Resource Consumption (CPU)

Mitigation: Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

Weakness & attack patterns

CWE-120Classic Buffer Overflow

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-10 · Buffer Overflow via Environment VariablesCAPEC-100 · Overflow BuffersCAPEC-14 · Client-side Injection-induced Buffer OverflowCAPEC-24 · Filter Failure through Buffer OverflowCAPEC-42 · MIME ConversionCAPEC-44 · Overflow Binary Resource FileCAPEC-45 · Buffer Overflow via Symbolic LinksCAPEC-46 · Overflow Variables and TagsCAPEC-47 · Buffer Overflow via Parameter ExpansionCAPEC-67 · String Format Overflow in syslog()CAPEC-8 · Buffer Overflow in an API CallCAPEC-9 · Buffer Overflow in Local Command-Line Utilities

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable VigorSwitch G2540xs, VigorSwitch P2540xs, VigorSwitch FX2120, VigorSwitch G2282x, VigorSwitch P2282x, VigorSwitch Q2300x, VigorSwitch PQ2300xb, VigorSwitch G2542x, VigorSwitch P2542x, VigorSwitch P2542xh, VigorSwitch PX2060, VigorSwitch G1280, VigorSwitch P1280, VigorSwitch P1281x, VigorSwitch G1282, VigorSwitch P1282, VigorSwitch G2121, VigorSwitch P2121, VigorSwitch PQ2121x, VigorSwitch Q2121x, VigorSwitch G2280x, VigorSwitch P2280x, VigorSwitch Q2200x, VigorSwitch PQ2200xb, VigorSwitch G2100, VigorSwitch P2100, VigorSwitch G2540x, VigorSwitch P2540x.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 7.2 (AV:N)
Aug 24, 2026 · NVD
Initial · CVE published
Aug 24, 2026 · NVD
Added · GHSA-v8w8-j3hm-5q73 published (high)
Aug 24, 2026 · GitHub Security Advisory

Source activity

Readings a source repeats on a schedule, counted rather than listed.

1×CVE modified by NIST, Modified, LinkAug 24, 2026 · SOCRadar CTI

References

4 on the record

www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/
Vendor Advisory
www.vulncheck.com/advisories/draytek-vigorswitch-multiple-models-buffer-overflow-via-sysreboot
Vendor Advisory, Mitre, NIST
nvd.nist.gov/vuln/detail/CVE-2026-71936
NVD
github.com/advisories/GHSA-v8w8-j3hm-5q73
Exploit, Third Party Advisory

Elsewhere on this site

DrayTek Corporationevery CVE for this vendor
Memory Corruptionsame class
CWE-120other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-71936 is DrayTek VigorSwitch Multiple Models Buffer Overflow via sysreboot, a high vulnerability affecting VigorSwitch G2540xs, VigorSwitch P2540xs, VigorSwitch FX2120, VigorSwitch G2282x, VigorSwitch P2282x, VigorSwitch Q2300x, VigorSwitch PQ2300xb, VigorSwitch G2542x, VigorSwitch P2542x, VigorSwitch P2542xh, VigorSwitch PX2060, VigorSwitch G1280, VigorSwitch P1280, VigorSwitch P1281x, VigorSwitch G1282, VigorSwitch P1282, VigorSwitch G2121, VigorSwitch P2121, VigorSwitch PQ2121x, VigorSwitch Q2121x, VigorSwitch G2280x, VigorSwitch P2280x, VigorSwitch Q2200x, VigorSwitch PQ2200xb, VigorSwitch G2100, VigorSwitch P2100, VigorSwitch G2540x, VigorSwitch P2540x from DrayTek Corporation. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-71936. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-71936. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 7.2 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.