What is the CVSS score of CVE-2021-38161?

CVE-2021-38161 has a CVSS 3.1 base score of 8.1 (High). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 1.9%.

Is there a patch available for CVE-2021-38161?

Yes, a patch is available for CVE-2021-38161. Update the affected software to the latest version immediately.

Traffic Server CVE-2021-38161

HIGH

Improper Authentication (CWE-287)

2021-11-03 security@apache.org

Authentication Bypass Apache Debian Debian Linux Traffic Server

8.1

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-287 OWASP Top 10:2025 A07:2025 - Authentication Failures ASVS 5.0 V6 - Authentication Authentication mechanism validation MITRE ATT&CK 2 techniques across 2 tactics: Defense Evasion, Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 8.1 (HIGH). Attack characteristics: network attack vector, high complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	A remote attacker could bypass authentication mechanisms to gain unauthorized access by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 1.9% exploitation probability (EPSS)

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AnalysisAI

Improper Authentication vulnerability in TLS origin verification of Apache Traffic Server allows for man in the middle attacks.0.0 to 8.0.8. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Implement multi-factor authentication, enforce strong password policies, use proven authentication frameworks.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Improper Authentication (CWE-287), which allows attackers to bypass authentication mechanisms to gain unauthorized access. Improper Authentication vulnerability in TLS origin verification of Apache Traffic Server allows for man in the middle attacks.0.0 to 8.0.8. Affected products include: Apache Traffic Server, Debian Debian Linux.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 8.1 HIGH

AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

Improper Authentication vulnerability in TLS origin verification of Apache Traffic Server allows for man in the middle attacks. This issue affects Apache Traffic Server 8.0.0 to 8.0.8.

Threat Intelligence Overview

EPSS Score

1.9%

Top 23% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 1.9%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +2

CVSS: +40

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:a:apache:traffic_server:*:*:*:*:*:*:*:*

cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

More in Traffic Server

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CVE-2023-44487 HIGH Act Now POC

7.5 Oct 10

Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour

CVE-2015-3249 CRITICAL Act Now

9.8 Oct 30

The HTTP/2 experimental feature in Apache Traffic Server 5.3.x before 5.3.1 allows remote attackers to cause a denial of

CVE-2014-3525 CRITICAL Act Now

10.0 Aug 22

Unspecified vulnerability in Apache Traffic Server 3.x through 3.2.5, 4.x before 4.2.1.1, and 5.x before 5.0.1 has unkno

CVE-2015-5206 CRITICAL Act Now

9.8 Sep 13

Unspecified vulnerability in the HTTP/2 experimental feature in Apache Traffic Server before 5.3.x before 5.3.2 has unkn

CVE-2015-5168 CRITICAL Act Now

9.8 Sep 13

Unspecified vulnerability in the HTTP/2 experimental feature in Apache Traffic Server 5.3.x before 5.3.2 has unknown imp

CVE-2014-3624 CRITICAL Act Now

9.8 Oct 30

Apache Traffic Server 5.1.x before 5.1.1 allows remote attackers to bypass access restrictions by leveraging failure to

CVE-2021-43082 CRITICAL Act Now

9.8 Nov 03

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in the stats-over-http plugin of Ap

CVE-2021-35474 CRITICAL Act Now

9.8 Jun 30

Stack-based Buffer Overflow vulnerability in cachekey plugin of Apache Traffic Server.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0

CVE-2020-1944 CRITICAL Act Now

9.8 Mar 23

There is a vulnerability in Apache Traffic Server 6.0.0 to 6.2.3, 7.0.0 to 7.1.8, and 8.0.0 to 8.0.5 with a smuggling at

CVE-2023-33934 CRITICAL Act Now

9.1 Aug 09

Improper Input Validation vulnerability in Apache Software Foundation Apache Traffic Server.2.1. Rated critical severity

CVE-2024-35296 HIGH This Week

8.2 Jul 26

Invalid Accept-Encoding header can cause Apache Traffic Server to fail cache lookup and force forwarding requests.0.0 th

CVE-2017-5659 HIGH This Week

7.5 Apr 17

Apache Traffic Server before 6.2.1 generates a coredump when there is a mismatch between content length and chunked enco

Same weakness CWE-287 – Improper Authentication

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CVE-2022-40684 CRITICAL POC

9.8

CVE-2025-61882 CRITICAL POC

9.8

CVE-2020-0688 HIGH POC

8.8

CVE-2023-46805 HIGH POC

8.2

CVE-2023-35078 CRITICAL POC

9.8

CVE-2015-1187 CRITICAL POC

9.8

CVE-2024-7593 CRITICAL POC

9.8

CVE-2017-7921 CRITICAL POC

9.8

Same technique Authentication Bypass

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CVE-2015-3306 CRITICAL POC

10.0

CVE-2023-22515 CRITICAL POC

9.8

CVE-2012-4681 CRITICAL POC

9.8

CVE-2013-2465 CRITICAL POC

9.8

CVE-2011-3544 CRITICAL POC

9.8

CVE-2024-0012 CRITICAL POC

9.3

References

Advisories & patches

PATCH https://lists.apache.org/thread/k01797hyncx53659wr3o72s5cvkc3164 REF https://www.debian.org/security/2022/dsa-5153

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