CVE-2021-42659Public exploit

Web service crash via unbounded list parsing

Published May 24, 2022 · Updated Aug 4, 2024

Buffer overflow in Tenda AC9 httpd 15.03.02.19(6318) and 15.03.06.42_multi allows remote attackers to crash the web server. The formSetVirtualSer handler passes the list field to sub_763EC, where unbounded sscanf conversions write attacker-controlled fields into fixed stack buffers and overwrite control data. Exploitation requires access to the neighboring network; one crafted virtual-service request terminates httpd, interrupting the router management service.

CVSS severity6.5
Medium
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Buffer overflow in Tenda AC9 httpd 15.03.02.19(6318) and 15.03.06.42_multi allows remote attackers to crash the web server. The formSetVirtualSer handler passes the list field to sub_763EC, where unbounded sscanf conversions write attacker-controlled fields into fixed stack buffers and overwrite control data. Exploitation requires access to the neighboring network; one crafted virtual-service request terminates httpd, interrupting the router management service.

The record

CVE
CVE-2021-42659
Published
May 24, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 24, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.1NVDAV:A/AC:L/Au:N/C:N/I:N/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo