Router firmware: Stack-based Buffer Overflow
CVE-2026-84730 is a high-severity stack-based buffer overflow vulnerability in Router firmware from ASUS, with a CVSS 4.0 base score of 8.7 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. Affected Router firmware versions: ASUSWRT 3.0.0.4_386 series; ASUSWRT 3.0.0.4_388 series; ASUSWRT 3.0.0.6_102 series. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.34% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Router firmware you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on asus.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| ASUS | Router firmware | ASUSWRT 3.0.0.4_386 series; ASUSWRT 3.0.0.4_388 series; ASUSWRT 3.0.0.6_102 series | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- NoneNo loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- NoneNo loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- NoneNo loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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. Scored by CNA.
Official description
Stack-based buffer overflow in certain ASUS Router firmware allows an unauthenticated nearby attacker to execute arbitrary commands with root privileges via a crafted device name. Refer to the ' Security Update for ASUS Router AiCloud Feature ' section on the ASUS Security Advisory for more information.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Stack-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the stack.
How developers prevent this class of flaw
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Implement and perform bounds checking on input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Router firmware
- 8.7 High severity
- 7.0 High severity
- 7.1 High severity
- 7.2 High severity
Recent Stack-based Buffer Overflow vulnerabilities
- 7.4 High severity
- 7.1 High severity
- 7.3 High severity
- 9.6 Critical severity
- 7.5 High severity
- 8.8 High severity
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