What’s Vulnerable › Vulnerabilities

CVE-2021-25761

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-03 · updated 2026-06-17
• Weakness: CWE-326

Description

In JetBrains Ktor before 1.5.0, a birthday attack on SessionStorage key was possible.

Affected products

• JetBrains Ktor: before 1.5.0 — fixed in 1.5.0

How to fix

Upgrade to a fixed version: JetBrains Ktor 1.5.0. Check the vendor advisory for mitigations.

References

• https://blog.jetbrains.com
• https://blog.jetbrains.com/blog/2021/02/03/jetbrains-security-bulletin-q4-2020/
• https://blog.jetbrains.com
• https://blog.jetbrains.com/blog/2021/02/03/jetbrains-security-bulletin-q4-2020/

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