ATS negative cache option is vulnerable to a cache poisoning attack.

published 2021-01-11 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-9457

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.8%; EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits: 0; none known

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.

Patch / fix

distros 1

trafficserver Debian 12 8.1.1+ds-1

debian advisories DEBIAN-CVE-2020-17509

Exploit prediction

1.81% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

n/a Apache Traffic Server

Classification

Weakness

CWE-444 Inconsistent Interpretation of HTTP Requests

References

lists.apache.org /thread.html/raa9f0589c26c4d146646425e51e2a33e1457492df9f7ea2019daa6d3%40%3Cannounce.trafficserver.apache.org%
mailing-list, vendor-advisory

Sources

CVE List CVE-2020-17509
NVD CVE-2020-17509

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary