What’s Vulnerable › Vulnerabilities

CVE-2021-43203

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-09 · updated 2026-06-17
• Weakness: CWE-287

Description

In JetBrains Ktor before 1.6.4, nonce verification during the OAuth2 authentication process is implemented improperly.

Affected products

• JetBrains Ktor: before 1.6.4 — fixed in 1.6.4

How to fix

Upgrade to a fixed version: JetBrains Ktor 1.6.4. Check the vendor advisory for mitigations.

References

• https://blog.jetbrains.com/blog/2021/11/08/jetbrains-security-bulletin-q3-2021/
• https://blog.jetbrains.com/blog/2021/11/08/jetbrains-security-bulletin-q3-2021/

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