CVE-2026-76216: Vikunja through 2.4.0 Principal-Type Confusion via LinkSharing

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-19 · updated 2026-09-16
Weakness: CWE-639

Description

Vikunja through 2.4.0 contains a principal-type confusion vulnerability where LinkSharing principals with id N are treated as user principals with users.id == N at three permission checks lacking type guards. Attackers with a link-share JWT can remove victims from teams, enumerate and delete victim bot users, or read team rosters by exploiting id collisions in the autoincrement space.

Affected products

go-vikunja vikunja: through 2.4.0

References

https://github.com/go-vikunja/vikunja/security/advisories/GHSA-32r8-5843-4qw2
https://www.vulncheck.com/advisories/vikunja-through-principal-type-confusion-via-linksharing

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