CVE-2020-17509Network attack vector

Cache poisoning via overbroad response cacheability

Published Jan 11, 2021 · Updated Aug 4, 2024

Improper response caching in Apache Traffic Server 7.0.0 through 7.1.11 and 8.0.0 through 8.1.0 allows remote attackers to poison caches. When negative caching is enabled, HttpTransact::is_response_cacheable treats nearly every response status as cacheable instead of limiting storage to configured negative codes. Unauthenticated network access and the nondefault option are required; poisoned entries can make later clients receive attacker-influenced responses.

CVSS severity7.5
High
EPSS probability1.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper response caching in Apache Traffic Server 7.0.0 through 7.1.11 and 8.0.0 through 8.1.0 allows remote attackers to poison caches. When negative caching is enabled, HttpTransact::is_response_cacheable treats nearly every response status as cacheable instead of limiting storage to configured negative codes. Unauthenticated network access and the nondefault option are required; poisoned entries can make later clients receive attacker-influenced responses.

The record

CVE
CVE-2020-17509
Published
Jan 11, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache Traffic Server
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 11, 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=Apache Traffic Server 7.0.0 to 7.1.11, 8.0.0 to 8.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Traffic Serverversion=Apache Traffic Server 7.0.0 to 7.1.11, 8.0.0 to 8.1.0

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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