CVE-2021-41585Network attack vector

Connection refusal via improper socket input validation

Published Nov 3, 2021 · Updated Aug 4, 2024

Denial of service in Apache Traffic Server 5.0.0 through 9.1.0 on FreeBSD allows remote attackers to stop acceptance of new connections. The published description locates the flaw in socket-connection acceptance but does not specify the malformed input or exact failed validation check. The condition is FreeBSD-specific and affects availability only, leaving the proxy unable to accept additional clients without granting data access or modification.

CVSS severity7.5
High
EPSS probability2.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Apache Traffic Server 5.0.0 through 9.1.0 on FreeBSD allows remote attackers to stop acceptance of new connections. The published description locates the flaw in socket-connection acceptance but does not specify the malformed input or exact failed validation check. The condition is FreeBSD-specific and affects availability only, leaving the proxy unable to accept additional clients without granting data access or modification.

The record

CVE
CVE-2021-41585
Published
Nov 3, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache Traffic Server
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 3, 2021CVE 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

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=7.0.0 to 9.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Traffic Serverversion=7.0.0 to 9.1.0

Published CVSS scores

7.5CanonicalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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