CVE-2021-20217: A flaw was found in Privoxy in versions before 3.0.31

Q: How do I fix CVE-2021-20217?

privoxy: upgrade to 3.0.31. Exact commands for each OS are on this page.

Q: Is CVE-2021-20217 being exploited?

CVE-2021-20217 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-20217 affect?

CVE-2021-20217 affects privoxy. Severity is high (CVSS 7.5). A flaw was found in Privoxy in versions before 3.0.31. An assertion failure triggered by a crafted CGI request may lead to denial of service. The highest threat from this vulnerability is to system availability.

Q: How urgent is CVE-2021-20217?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2021-20217 is a high-severity flaw (CVSS 7.5) affecting privoxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in Privoxy in versions before 3.0.31. An assertion failure triggered by a crafted CGI request may lead to denial of service. The highest threat from this vulnerability is to system availability.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 28%)
CISA exploited list	No
Weakness	CWE-617
Published	2021-03-25
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: privoxy

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-03-25 19:15 UTCPublished CVE record published
2026-06-17 03:33 UTCUpdated Record last modified

privoxy privoxy UPGRADE

Affected: < 3.0.31

Fixed in: 3.0.31

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy privoxy || rpm -q privoxy || privoxy --version

2. UPGRADE to 3.0.31 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade privoxy

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade privoxy

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-20217?

privoxy: upgrade to 3.0.31. Exact commands for each OS are on this page.

Is CVE-2021-20217 being exploited?

CVE-2021-20217 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-20217 affect?

CVE-2021-20217 affects privoxy. Severity is high (CVSS 7.5). A flaw was found in Privoxy in versions before 3.0.31. An assertion failure triggered by a crafted CGI request may lead to denial of service. The highest threat from this vulnerability is to system availability.

How urgent is CVE-2021-20217?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-44543 MEDIUM 6.1 UPGRADE An XSS vulnerability was found in Privoxy which was fixed in cgi_error_no_template() by encode the template na
CVE-2021-44542 HIGH 7.5 UPGRADE A memory leak vulnerability was found in Privoxy when handling errors.
CVE-2021-44541 HIGH 7.5 UPGRADE A vulnerability was found in Privoxy which was fixed in process_encrypted_request_headers() by freeing header
CVE-2021-44540 HIGH 7.5 UPGRADE A vulnerability was found in Privoxy which was fixed in get_url_spec_param() by freeing memory of compiled pat
CVE-2021-20276 HIGH 7.5 UPGRADE MITIGATE A flaw was found in privoxy before 3.0.32

References

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