CVE-2021-31718Public exploitNetwork attack vector

Remote code execution via unchecked Host header

Published Apr 25, 2021 · Updated Aug 3, 2024

DNS rebinding in npupnp before 4.1.4 allows remote attackers to execute code through the embedded UPnP web server. The server accepts domain names in the HTTP Host header without validating them against a local interface, enabling browser-originated SOAP or GENA requests after rebinding. A user must visit attacker-controlled content served on the UPnP port; exposed service actions determine the resulting data access, state change, or code execution.

CVSS severity8.8
High
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS rebinding in npupnp before 4.1.4 allows remote attackers to execute code through the embedded UPnP web server. The server accepts domain names in the HTTP Host header without validating them against a local interface, enabling browser-originated SOAP or GENA requests after rebinding. A user must visit attacker-controlled content served on the UPnP port; exposed service actions determine the resulting data access, state change, or code execution.

The record

CVE
CVE-2021-31718
Published
Apr 25, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-346, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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-346Origin Validation Error
T1189Drive-by Compromise

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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