{"id":"CVE-2026-91972","aliases":["EUVD-2026-78648","GHSA-6rvj-qwjf-3m4q","GHSA-m4vj-wr5q-cmvr","GO-2026-6721"],"status":"published","title":"Vikunja before 2.6.0 Authentication Bypass via Unthrottled API","description":"Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","severity":{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00633,"percentile":0.50649,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-307"],"published":"2026-09-15T15:18:22Z","modified":"2026-10-28T02:31:08Z","fixes":[{"ecosystem":"Go","package":"code.vikunja.io/api","fixed_in":["2.6.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Go","package":"code.vikunja.io/api","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"2.5.0"},{"fixed":"2.6.0"}]}]},{"source":"osv","ecosystem":"Go","package":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.6.0"}]}]},{"source":"osv","ecosystem":"Go","package":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}]}],"products":[{"vendor":"go-vikunja","product":"vikunja"}],"references":[{"url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-6rvj-qwjf-3m4q","tags":["vendor-advisory","exploit","advisory","web"]},{"url":"https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-unthrottled-api","tags":["third-party-advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91972","tags":["advisory"]},{"url":"https://github.com/go-vikunja/vikunja/releases/tag/v2.6.0","tags":["web"]},{"url":"https://github.com/advisories/GHSA-6rvj-qwjf-3m4q"},{"url":"https://github.com/advisories/GHSA-m4vj-wr5q-cmvr"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91972.json","tags":["advisory"]},{"url":"https://github.com/go-vikunja/vikunja","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-91972","title":"Vikunja before 2.6.0 Authentication Bypass via Unthrottled API","description":"Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"published","published":"2026-09-15T15:18:22.792Z","modified":"2026-09-17T15:12:40.377Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T14:19:52.773089Z"}],"euvd":[{"id":"EUVD-2026-78648","description":"Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"published","published":"2026-09-15T15:18:22Z","modified":"2026-09-17T15:12:40Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T17:28:11.615612Z"}],"ghsa":[{"id":"GHSA-6rvj-qwjf-3m4q","title":"Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited","description":"### Summary\n`registerAPIRoutesV2` never applies the unconditional pre-auth rate-limit floor (`unauthRateLimit()`) to the v2 public routes — it passes that limiter only to `/api/v2/ws` — and otherwise relies on `setupRateLimit`, which registers nothing when `ratelimit.enabled` is false (the default). So on a stock install every v2 pre-auth endpoint (login, register, password-reset token, oauth token) is unthrottled, while its v1 twin is throttled.\n\n### Details\n`unauthRateLimit()` -\u003e `perMinuteIPRateLimit(\"noauth\", RateLimitNoAuthRoutesLimit)` (`pkg/routes/rate_limit.go`, ~lines 100-118) is an unconditional per-IP floor (default 10/60s) that deliberately ignores `RateLimitEnabled`, which is why v1's pre-auth routes are throttled even with the global limiter off. v1 applies it: `ur := a.Group(\"\"); ur.Use(unauthRateLimit())` (`pkg/routes/routes.go` ~line 459). `registerAPIRoutesV2` (~lines 405-431) passes the `unauthRateLimit()` instance only to `/api/v2/ws`; its auth routes get only `setupRateLimit(a, ...)`, which is config-gated and registers nothing by default.\n\n### PoC (verified at runtime against v2.5.0)\n```\nPOST /api/v1/login              x25 -\u003e 429 from attempt 5\nPOST /api/v2/login              x25 -\u003e 403 x25, 429 x0\nPOST /api/v1/user/password/token     -\u003e 429 (throttled)\nPOST /api/v2/user/password/token x20 -\u003e 404 x20, 429 x0\n```\nRequest bodies are byte-identical across versions (shared `user.Login` / `user.PasswordTokenRequest`). Both v2 endpoints reach their handlers (403/404, not route-404), so the comparison is valid.\n\n### Impact\nThe pre-auth rate-limit floor — the instance's only default anti-brute-force / anti-abuse control — is absent on all v2 public endpoints. Enables unbounded credential guessing, account-enumeration probing, and password-reset flooding on a default install. Reported as an authentication-control bypass, not a DoS.\n\n### Fix\nApply `unauthRateLimit()` to the v2 public route group, matching v1.","status":"published","published":"2026-10-09T20:51:05Z","modified":"2026-10-09T20:51:07Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T14:41:31.175024Z"},{"id":"GHSA-m4vj-wr5q-cmvr","title":"Duplicate Advisory: Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited","description":"### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-6rvj-qwjf-3m4q. This link is maintained to preserve external references.\n\n### Original Description\nVikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"withdrawn","published":"2026-09-15T18:32:30Z","modified":"2026-10-09T20:51:00Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T14:41:31.175024Z"}],"nvd":[{"id":"CVE-2026-91972","description":"Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"published","published":"2026-09-15T16:17:54.087Z","modified":"2026-09-17T16:18:32.093Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high","assessor":"secondary"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T14:12:47.668237Z"}],"osv":[{"id":"CVE-2026-91972","title":"Vikunja before 2.6.0 Authentication Bypass via Unthrottled API","description":"Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"published","published":"2026-09-15T15:18:22.792Z","modified":"2026-10-28T02:31:08.740568657Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T15:45:20.269367Z"},{"id":"GHSA-6rvj-qwjf-3m4q","title":"Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited","description":"### Summary\n`registerAPIRoutesV2` never applies the unconditional pre-auth rate-limit floor (`unauthRateLimit()`) to the v2 public routes — it passes that limiter only to `/api/v2/ws` — and otherwise relies on `setupRateLimit`, which registers nothing when `ratelimit.enabled` is false (the default). So on a stock install every v2 pre-auth endpoint (login, register, password-reset token, oauth token) is unthrottled, while its v1 twin is throttled.\n\n### Details\n`unauthRateLimit()` -\u003e `perMinuteIPRateLimit(\"noauth\", RateLimitNoAuthRoutesLimit)` (`pkg/routes/rate_limit.go`, ~lines 100-118) is an unconditional per-IP floor (default 10/60s) that deliberately ignores `RateLimitEnabled`, which is why v1's pre-auth routes are throttled even with the global limiter off. v1 applies it: `ur := a.Group(\"\"); ur.Use(unauthRateLimit())` (`pkg/routes/routes.go` ~line 459). `registerAPIRoutesV2` (~lines 405-431) passes the `unauthRateLimit()` instance only to `/api/v2/ws`; its auth routes get only `setupRateLimit(a, ...)`, which is config-gated and registers nothing by default.\n\n### PoC (verified at runtime against v2.5.0)\n```\nPOST /api/v1/login              x25 -\u003e 429 from attempt 5\nPOST /api/v2/login              x25 -\u003e 403 x25, 429 x0\nPOST /api/v1/user/password/token     -\u003e 429 (throttled)\nPOST /api/v2/user/password/token x20 -\u003e 404 x20, 429 x0\n```\nRequest bodies are byte-identical across versions (shared `user.Login` / `user.PasswordTokenRequest`). Both v2 endpoints reach their handlers (403/404, not route-404), so the comparison is valid.\n\n### Impact\nThe pre-auth rate-limit floor — the instance's only default anti-brute-force / anti-abuse control — is absent on all v2 public endpoints. Enables unbounded credential guessing, account-enumeration probing, and password-reset flooding on a default install. Reported as an authentication-control bypass, not a DoS.\n\n### Fix\nApply `unauthRateLimit()` to the v2 public route group, matching v1.","status":"published","published":"2026-10-09T20:51:05Z","modified":"2026-10-19T21:41:17.124911538Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T15:46:39.965326Z"},{"id":"GHSA-m4vj-wr5q-cmvr","title":"Duplicate Advisory: Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited","description":"### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-6rvj-qwjf-3m4q. This link is maintained to preserve external references.\n\n### Original Description\nVikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.","status":"withdrawn","published":"2026-09-15T18:32:30Z","modified":"2026-10-09T21:00:06.429398765Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high"},{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"}],"cwes":["CWE-307"],"updated_at":"2026-11-02T15:46:51.463834Z"},{"id":"GO-2026-6721","title":"Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited in code.vikunja.io/api","description":"Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited in code.vikunja.io/api.\n\nNOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.\n\n(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)\n\nThe additional affected modules and versions are: code.vikunja.io/api before v2.6.0.","status":"published","published":"2026-10-19T21:08:26Z","modified":"2026-10-19T21:31:52.274584795Z","updated_at":"2026-11-02T15:47:03.11707Z"}]}}