CVE-2020-17509

ATS negative cache option is vulnerable to a cache poisoning attack. If you have this option...

7.5 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: High
Availability: None

Exploit likelihood

1.81%Up 0.6 points since Apr 14, 2021

What each source reports

NVD Score used 7.5

Record: CVE-2020-17509
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 2.0: 4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness: CWE-444
Updated: 2026-11-02

CVE List No score

Record: CVE-2020-17509
Updated: 2026-11-02

EUVDEUVD-2020-9457 No score

Record: EUVD-2020-9457
Updated: 2026-11-03

GitHub AdvisoriesGHSA-wgc8-c98w-8fvh No score

ATS negative cache option is vulnerable to a cache poisoning attack. If you have this option...

Record: GHSA-wgc8-c98w-8fvh
Weakness: CWE-444
Updated: 2026-11-02

OSV 7.5

Record: CVE-2020-17509
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

OSVDEBIAN-CVE-2020-17509 7.5

Record: DEBIAN-CVE-2020-17509
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2020-17509 7.5

Record: UBUNTU-CVE-2020-17509
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`trafficserver` Debian:12	before 8.1.1+ds-1	8.1.1+ds-1
`trafficserver` Debian:10 From an advisory covering 2 CVEs	before 8.0.2+ds-1+deb10u4, plus listed versions 8.0.2+ds-18.0.2+ds-1+deb10u18.0.2+ds-1+deb10u28.0.2+ds-1+deb10u3	8.0.2+ds-1+deb10u4
`trafficserver` Ubuntu:16.04:LTS	All versions, plus listed versions 5.3.0-2ubuntu15.3.0-2ubuntu2	None known
`trafficserver` Ubuntu:18.04:LTS	All versions, plus listed versions 7.0.0-57.1.2+ds-27.1.2+ds-2build17.1.2+ds-3	None known
`trafficserver` Ubuntu:Pro:20.04:LTS	All versions, plus listed versions 8.0.5+ds-18.0.5+ds-28.0.5+ds-2build18.0.5+ds-2ubuntu18.0.5+ds-38.0.5+ds-3ubuntu0.1~esm1	None known

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 3, 2026	aliases, products	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-17509 is a high vulnerability (CVSS 7.5) in Apache Traffic Server, published December 7, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.81%, the 78th percentile. Fixed in trafficserver 8.1.1+ds-1.