CVE-2021-20211

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active...

7.5 HighFix available

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

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

2.15%Up 1.5 points since Apr 14, 2021

What each source reports

NVD Score used 7.5

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: CVE-2021-20211
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: 7.8 HighAV:N/AC:L/Au:N/C:N/I:N/A:C
Weakness: CWE-401
Updated: 2026-11-02

CVE List No score

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: CVE-2021-20211
Weakness: CWE-401
Updated: 2026-11-02

EUVDEUVD-2021-7654 No score

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: EUVD-2021-7654
Updated: 2026-11-03

GitHub AdvisoriesGHSA-vpp2-6qww-77r8 No score

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active...

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: GHSA-vpp2-6qww-77r8
Weakness: CWE-401
Updated: 2026-11-02

OSVALPINE-CVE-2021-20211 7.5

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: ALPINE-CVE-2021-20211
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

OSV 7.5

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: CVE-2021-20211
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-2021-20211 7.5

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: DEBIAN-CVE-2021-20211
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-2021-20211 7.5

A flaw was found in Privoxy in versions before 3.0.29. Memory leak when client tags are active can cause a system crash.

Record: UBUNTU-CVE-2021-20211
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

OSVUSN-4886-1 No score

privoxy vulnerabilities

It was discovered that Privoxy incorrectly handled CGI requests. An attacker could possibly use this issue to cause a denial of service or obtain sensitive information. (CVE-2020-35502, CVE-2021-20209, CVE-2021-20210, CVE-2021-20213, CVE-2021-20215, CVE-2021-20216, CVE-2021-20217, CVE-2021-20272, CVE-2021-20273, CVE-2021-20275)

It was discovered that Privoxy incorrectly handled certain regular expressions. An attacker could possibly use this issue to cause a denial of service or obtain sensitive information. (CVE-2021-20212, CVE-2021-20276)

It was discovered that Privoxy incorrectly handled client tags. An attacker could possibly use this issue to cause Privoxy to consume resources, resulting in a denial of service. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS and Ubuntu 20.10. (CVE-2021-20211)

Record: USN-4886-1
Updated: 2026-11-02

Affected products

privoxy

Affected packages

Affected packages
Package	Affected	Fixed
`privoxy` Alpine:v3.12	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.13	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.14	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.15	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.16	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.17	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.18	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.19	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.20	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.21	before 3.0.29-r0	3.0.29-r0

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Affected packages
Package	Affected	Fixed
`privoxy` Alpine:v3.22	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.23	before 3.0.29-r0	3.0.29-r0
`privoxy` Alpine:v3.24	before 3.0.29-r0	3.0.29-r0
`privoxy` Debian:12	before 3.0.29-1	3.0.29-1
`privoxy` Debian:13	before 3.0.29-1	3.0.29-1
`privoxy` Debian:14	before 3.0.29-1	3.0.29-1
`privoxy` Debian:9 From an advisory covering 9 CVEs	before 3.0.26-3+deb9u1, plus listed versions 3.0.26-3	3.0.26-3+deb9u1
`privoxy` Ubuntu:18.04:LTS	before 3.0.26-5ubuntu0.1, plus listed versions 3.0.26-33.0.26-43.0.26-5	3.0.26-5ubuntu0.1
`privoxy` Ubuntu:20.04:LTS	before 3.0.28-2ubuntu0.1, plus listed versions 3.0.28-2	3.0.28-2ubuntu0.1
`privoxy` Ubuntu:Pro:14.04:LTS From an advisory covering 14 CVEs	before 3.0.21-7+deb8u1ubuntu0.1~esm1, plus listed versions 3.0.21-13.0.21-23.0.21-7+deb8u1build0.14.04.1	3.0.21-7+deb8u1ubuntu0.1~esm1
`privoxy` Ubuntu:16.04:LTS From an advisory covering 14 CVEs	before 3.0.24-1ubuntu0.1, plus listed versions 3.0.23-33.0.23-43.0.23-53.0.24-1	3.0.24-1ubuntu0.1
`privoxy` Ubuntu:18.04:LTS From an advisory covering 14 CVEs	before 3.0.26-5ubuntu0.1, plus listed versions 3.0.26-33.0.26-43.0.26-5	3.0.26-5ubuntu0.1
`privoxy` Ubuntu:20.04:LTS From an advisory covering 14 CVEs	before 3.0.28-2ubuntu0.1, plus listed versions 3.0.28-2	3.0.28-2ubuntu0.1

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-2021-20211 is a high vulnerability (CVSS 7.5) in Privoxy, published February 3, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.15%, the 82nd percentile. Fixed in privoxy 3.0.29-r0.

References

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