What is CVE-2021-32816?

CVE-2021-32816 is a medium-severity vulnerability in Protonmail, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2021-05-14.

How severe is CVE-2021-32816?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Resource exhaustion in Protonmail

CVE-2021-32816

ProtonMail Web Client is the official AngularJS web client for the ProtonMail secure email service. ProtonMail Web Client before version 3.16.60 has a regular expression denial-of-service vulnerability. This was fixed in commit 6687fb. There is a full report available in the referenced GHSL-2021-027.

Vulnerability class: DoS (Denial of Service)

Published 2021-05-14 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.010 (61.7th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 61.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Protonmail
Protonmail Webclient — versions < 3.16.60

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

securitylab.github.com/advisories/GHSL-2021-027-redos-ProtonMail/ (Exploit, Third Party Advisory)
github.com/ProtonMail/WebClient/commit/6687fbb867ef872c96cf4fde68cb6e9c58d3fddc (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-32816?: CVE-2021-32816 is a medium-severity vulnerability in Protonmail, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2021-05-14.
How severe is CVE-2021-32816?: Medium severity. CVSS v3 base score is 6.5 out of 10.