How severe is CVE-2020-17509?

CVE-2020-17509 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2020-17509 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-17509?

CVE-2020-17509 affects Apache Traffic Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-17509?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-17509 published?

CVE-2020-17509 was published on 2021-01-11 and last updated on 2026-06-17.

CVE-2020-17509

CVE-2020-17509 is a high-severity vulnerability in Apache Traffic Server with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-444.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 4.3
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Apache Traffic Server
Published: 2021-01-11
Last modified: 2026-06-17

Description

ATS negative cache option is vulnerable to a cache poisoning attack. If you have this option enabled, please upgrade or disable this feature. Apache Traffic Server versions 7.0.0 to 7.1.11 and 8.0.0 to 8.1.0 are affected.

Frequently asked questions

What is CVE-2020-17509?: ATS negative cache option is vulnerable to a cache poisoning attack. If you have this option enabled, please upgrade or disable this feature. Apache Traffic Server versions 7.0.0 to 7.1.11 and 8.0.0 to 8.1.0 are affected.
How severe is CVE-2020-17509?: CVE-2020-17509 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2020-17509 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-17509?: CVE-2020-17509 affects Apache Traffic Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-17509?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-17509 published?: CVE-2020-17509 was published on 2021-01-11 and last updated on 2026-06-17.

References

https://lists.apache.org/thread.html/raa9f0589c26c4d146646425e51e2a33e1457492df9f7ea2019daa6d3%40%3Cannounce.trafficserver.apache.org%3E

Affected products (1)

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

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