What’s Vulnerable › Vulnerabilities

CVE-2021-32816: Regular expression Denial of Service in ProtonMail

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-05-14 · updated 2026-06-17
• Weakness: CWE-400

Description

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.

Affected products

• Protonmail: before 3.16.60 — fixed in 3.16.60

How to fix

Upgrade to a fixed version: Protonmail 3.16.60. Check the vendor advisory for mitigations.

References

• https://github.com/ProtonMail/WebClient/commit/6687fbb867ef872c96cf4fde68cb6e9c58d3fddc
• https://securitylab.github.com/advisories/GHSL-2021-027-redos-ProtonMail/
• https://github.com/ProtonMail/WebClient/commit/6687fbb867ef872c96cf4fde68cb6e9c58d3fddc
• https://securitylab.github.com/advisories/GHSL-2021-027-redos-ProtonMail/

Get alerted when CVE-2021-32816 or the next vulnerability affects your stack