CVE-2021-32566

Specific sequence of HTTP/2 frames can cause ATS to crash

7.5 HighFix available

Improper Input Validation vulnerability in HTTP/2 of Apache Traffic Server allows an attacker to DOS the server. This issue affects Apache Traffic Server 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0.0 to 9.0.1.

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: None
Availability: High

Exploit likelihood

2.45%Up 2.0 points since Jun 30, 2021

What each source reports

NVD Score used 7.5

Record: CVE-2021-32566
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-20
Updated: 2026-11-02

CVE List No score

Specific sequence of HTTP/2 frames can cause ATS to crash

Record: CVE-2021-32566
Weakness: CWE-20
Updated: 2026-11-02

EUVDEUVD-2021-19408 No score

Record: EUVD-2021-19408
Updated: 2026-11-03

GitHub AdvisoriesGHSA-8cqh-mhwj-8g3v No score

Improper Input Validation vulnerability in HTTP/2 of Apache Traffic Server allows an attacker to...

Record: GHSA-8cqh-mhwj-8g3v
Weakness: CWE-20
Updated: 2026-11-02

OSV 7.5

Record: CVE-2021-32566
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-32566 7.5

Record: DEBIAN-CVE-2021-32566
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-32566 7.5

Record: UBUNTU-CVE-2021-32566
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`trafficserver` Debian:12	before 8.1.1+ds-1.1	8.1.1+ds-1.1
`trafficserver` Debian:10 From an advisory covering 5 CVEs	before 8.0.2+ds-1+deb10u5, plus listed versions 8.0.2+ds-18.0.2+ds-1+deb10u18.0.2+ds-1+deb10u28.0.2+ds-1+deb10u38.0.2+ds-1+deb10u4	8.0.2+ds-1+deb10u5
`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	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-2021-32566 is a high vulnerability (CVSS 7.5) in Apache Traffic Server, published June 30, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.45%, the 84th percentile. Fixed in trafficserver 8.1.1+ds-1.1.

References

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