What is CVE-2021-3116?

CVE-2021-3116 is a high-severity vulnerability in Proxy.py Project, classified under Incorrect Comparison. CVSS score: 7.5/10. Published 2021-01-11.

How severe is CVE-2021-3116?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Proxy.py Project

CVE-2021-3116

before_upstream_connection in AuthPlugin in http/proxy/auth.py in proxy.py before 2.3.1 accepts incorrect Proxy-Authorization header data because of a boolean confusion (and versus or).

Published 2021-01-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.017 (76.7th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 76.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: +0.000

Affected products

Proxy.py Project

Weakness classification (CWE)

CWE-697 — Incorrect Comparison

References

cardaci.xyz/advisories/2021/01/10/proxy.py-2.3.0-broken-basic-authentication/ (Exploit, Third Party Advisory)
github.com/abhinavsingh/proxy.py/pull/482/commits/9b00093288237f5073c403f2c4f62… (Patch)
pypi.org/project/proxy.py/2.3.1/ (Product)

Frequently asked questions

What is CVE-2021-3116?: CVE-2021-3116 is a high-severity vulnerability in Proxy.py Project, classified under Incorrect Comparison. CVSS score: 7.5/10. Published 2021-01-11.
How severe is CVE-2021-3116?: High severity. CVSS v3 base score is 7.5 out of 10.