CVE-2021-3116Public exploitNetwork attack vector

Unauthenticated proxy access via boolean logic error

Published Jan 11, 2021 · Updated Aug 3, 2024

Authentication bypass in proxy.py before 2.3.1 allows remote attackers to relay proxy requests by supplying any basic credentials. AuthPlugin.before_upstream_connection joins three rejection tests with AND, so a two-part Basic header suppresses rejection even when its credential token is wrong. Exploitation requires basic authentication to be enabled and grants unauthorized use of the configured HTTP proxy.

CVSS severity8.7
High
EPSS probability1.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in proxy.py before 2.3.1 allows remote attackers to relay proxy requests by supplying any basic credentials. AuthPlugin.before_upstream_connection joins three rejection tests with AND, so a two-part Basic header suppresses rejection even when its credential token is wrong. Exploitation requires basic authentication to be enabled and grants unauthorized use of the configured HTTP proxy.

The record

CVE
CVE-2021-3116
Published
Jan 11, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-697, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 11, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.7GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

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 exploitPublished

Weakness, pattern, technique

CWE-697Incorrect Comparison
T1190Exploit Public-Facing Application

Public exploit references

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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