CVE-2021-20209Network attack vector

Service interruption via unreleased show-status allocation

Published May 25, 2021 · Updated Aug 3, 2024

Memory leak in Privoxy before 3.0.29 allows remote attackers to exhaust service memory through the show-status CGI endpoint. The cgi_show_status no-action-files branch leaves its allocated status string unreleased after mapping the empty-list response. An attacker must reach the CGI interface on an instance with no action files configured; repeated requests can exhaust memory and interrupt service.

CVSS severity7.5
High
EPSS probability1.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in Privoxy before 3.0.29 allows remote attackers to exhaust service memory through the show-status CGI endpoint. The cgi_show_status no-action-files branch leaves its allocated status string unreleased after mapping the empty-list response. An attacker must reach the CGI interface on an instance with no action files configured; repeated requests can exhaust memory and interrupt service.

The record

CVE
CVE-2021-20209
Published
May 25, 2021
Updated
Aug 3, 2024
Vendor
Privoxy Developers
Product
Privoxy
Classifications
CWE-401, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=before 3.0.29

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Privoxy Developers · Privoxyversion=before 3.0.29

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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