CVE-2021-34202Public exploit

Local code execution via nl_server overflow

Published Jun 16, 2021 · Updated Jul 9, 2026

Out-of-bounds write in D-Link DIR-2640 firmware 1.01B04 allows local users to execute arbitrary code via the nl_server process. The process copies an unbounded user-controlled parameter into a stack buffer, overwriting the return address because defensive compilation protections are absent. Ordinary users can invoke nl_server to obtain root-level execution; remote code execution requires another flaw to control the bridge name externally.

CVSS severity7.8
High
EPSS probability3.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in D-Link DIR-2640 firmware 1.01B04 allows local users to execute arbitrary code via the nl_server process. The process copies an unbounded user-controlled parameter into a stack buffer, overwriting the return address because defensive compilation protections are absent. Ordinary users can invoke nl_server to obtain root-level execution; remote code execution requires another flaw to control the bridge name externally.

The record

CVE
CVE-2021-34202
Published
Jun 16, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.2NVDAV:L/AC:L/Au:N/C:C/I:C/A:C
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

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No observations available

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1068Exploitation for Privilege Escalation

Public exploit references

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

Technologies

Your stack

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Your stack

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