CVE-2020-25366Public exploitNetwork attack vector

Unauthenticated router crash via firmware upload

Published Nov 4, 2021 · Updated Jul 9, 2026

Missing authorization in D-Link DIR-823G REVA1 1.02B05 allows remote attackers to crash the router via a crafted firmware upload. The upload handler accepts an unauthenticated multipart POST, checks only the first four payload bytes for cs6c or cr6c, and passes the file into firmware processing. Reaching the management HTTP interface is required; the demonstrated consequence is loss of router service, not confirmed permanent damage.

CVSS severity9.1
Critical
EPSS probability2.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in D-Link DIR-823G REVA1 1.02B05 allows remote attackers to crash the router via a crafted firmware upload. The upload handler accepts an unauthenticated multipart POST, checks only the first four payload bytes for cs6c or cr6c, and passes the file into firmware processing. Reaching the management HTTP interface is required; the demonstrated consequence is loss of router service, not confirmed permanent damage.

The record

CVE
CVE-2020-25366
Published
Nov 4, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-862, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 4, 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.5NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:C
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-862Missing Authorization
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

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Your stack

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