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CVE-2021-3116

24
FAUCET Score

CVE-2021-3116 is a high-severity vulnerability affecting proxy.py versions prior to 2.3.1, where a boolean logic error in the AuthPlugin’s before_upstream_connection function allows incorrect Proxy-Authorization header data to be accepted. This network-exploitable flaw has a CVSS score of 7.5, indicating a high impact on integrity with no confidentiality or availability impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.3.1CPE matchmatch criteria
cpe:2.3:a:proxy.py_project:proxy.py:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.67%
Probability of exploitation in next 30 days
EPSS Percentile
74.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0167 is in the 57th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: proxy.pyFixed in: 2.3.1

Vendor Advisories (1)

pipGHSA-cmc7-mfmr-xqrxhigh

Logic error in authentication in proxy.py

Apr 7, 2021

References

cardaci.xyz / advisories/2021/01/10/proxy.py-2.3.0-broken-basic-authentication
ExploitThird Party Advisory
github.com / abhinavsingh/proxy.py/pull/482/commits/9b00093288237f5073c403f2c4f62acfdfa8ed46
Patch
pypi.org / project/proxy.py/2.3.1
Product