CVE-2021-3116

7.5 HIGH 2% exploit odds Fix listed

What it is

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).

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data tampering.
Exploit odds: 1.7% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2021-01-11 05:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 04:04 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 1.7% in the next 30 days (EPSS).
Severity: 7.5 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2021-01-11 05:15 UTC
Last modified: 2026-06-17 04:04 UTC
Exploit probability: 1.7% · EPSS, next 30 days
Weakness: CWE-697
Record status: Modified

Affected

proxy.py Project proxy.py < 2.3.1

Attack profile CVSS 3.1 · 7.5

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-3116.md and follow it. Check whether this project is affected by CVE-2021-3116. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record