What’s Vulnerable › Vulnerabilities

CVE-2026-48991: XianYuLauncher: Legacy Microsoft account OAuth sign-in flow lacks PKCE and state validation

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-17 · updated 2026-06-22
• Weakness: CWE-287

Description

XianYuLauncher is a Minecraft Java Edition launcher. In versions prior to 1.5.5, sensitive authentication artifacts could be exposed during a user-initiated login under certain local attack conditions. Affected versions relied on a fixed localhost redirect URI without PKCE or state validation. Exploitation is most likely to occur when an attacker is able to observe, intercept, or otherwise interfere with the local authentication flow on the same device. This issue has been fixed in version 1.5.5.

Affected products

• XianYuLauncher: before 1.5.5

References

• https://github.com/XianYuLauncher/XianYuLauncher/pull/213
• https://github.com/XianYuLauncher/XianYuLauncher/security/advisories/GHSA-q6r9-qxmf-8hfx

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