CVE-2021-44540Network attack vector

Service interruption via URL-pattern memory leak

Published Dec 23, 2021 · Updated Aug 4, 2024

A memory leak in Privoxy before 3.0.33 allows remote attackers to exhaust process memory through repeated URL-pattern parsing. The get_url_spec_param() error path abandons a compiled pattern specification without releasing its allocation. Unauthenticated network access is sufficient; repeated triggering can interrupt the proxy without affecting data confidentiality or integrity.

CVSS severity7.5
High
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A memory leak in Privoxy before 3.0.33 allows remote attackers to exhaust process memory through repeated URL-pattern parsing. The get_url_spec_param() error path abandons a compiled pattern specification without releasing its allocation. Unauthenticated network access is sufficient; repeated triggering can interrupt the proxy without affecting data confidentiality or integrity.

The record

CVE
CVE-2021-44540
Published
Dec 23, 2021
Updated
Aug 4, 2024
Vendor
Privoxy Developers
Product
Privoxy
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=Privoxy 3.0.33

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Privoxy Developers · Privoxyversion=Privoxy 3.0.33

Published CVSS scores

7.5UbuntuCVSS: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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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