CVE-2026-91981 — Vikunja before 2.6.0 User Enumeration via v2 API

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MEDIUM

Vikunja before 2.6.0 User Enumeration via v2 API

Published Sep 15, 2026

5.3

MEDIUM

CVSS 4.0

EPSS 0.31%

Description

Vikunja versions before 2.6.0 fail to properly validate link-share tokens in the v2 API user search endpoints. Attackers with a read-only share link can enumerate project users via the projects endpoint and confirm arbitrary usernames exist via the global search endpoint.

Affected products

Vendor GO-Vikunja Product Vikunja Default
unaffected
- Version
  0
  Status
  affected
  Constraints
  <2.6.0
- Version
  2.6.0
  Status
  unaffected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

GO-Vikunja

Vikunja

unaffected

Version	Status	Constraints
0	affected	<2.6.0
2.6.0	unaffected	-

Remediation

No remediation recorded yet.

Metrics

0.31% 0.00306

Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 3, 2026.

EPSS probability 0.00306

Score over time

Sep–Oct 2026

EPSS v5

Percentile over time

EPSS v5

Table of values (2 key points)

Flat stretches are collapsed; showing up to 120 newest points.

Date	Score	Percentile	Model
Oct 3, 2026	0.31% (0.00306)	21.27th	v5 (v2026.06.15)
Sep 16, 2026	0.24% (0.00241)	15.40th	v5 (v2026.06.15)

Weaknesses (1)

CWE-200

Exposure of Sensitive Information

References (2)

https://github.com/go-vikunja/vikunja/security/advisories/GHSA-vfxw-3x8p-2vjr
exploitvendor-advisory
https://www.vulncheck.com/advisories/vikunja-before-2.6.0-user-enumeration-via-v2-api
third-party-advisory

Link	Providers	Tags
https://github.com/go-vikunja/vikunja/security/advisories/GHSA-vfxw-3x8p-2vjr		exploitvendor-advisory
https://www.vulncheck.com/advisories/vikunja-before-2.6.0-user-enumeration-via-v2-api		third-party-advisory