Gitea Basic Auth bypasses OAuth2 access token scopes

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Gitea versions up to and including 1.26.1 allow OAuth2 access token scope enforcement to be bypassed through HTTP Basic authentication.

Source published

3 Jul 2026 20:19:38 UTC

Source modified

6 Jul 2026 15:18:39 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Gitea versions up to and including 1.26.1 allow OAuth2 access token scope enforcement to be bypassed through HTTP Basic authentication.

Source published

Jul 3, 2026, 8:19:38 PM (timezone not stated)

Source modified

Jul 6, 2026, 3:18:39 PM (timezone not stated)

Observed here

7 Nov 2026 06:34:02 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Gitea versions up to and including 1.26.1 allow OAuth2 access token scope enforcement to be bypassed through HTTP Basic authentication.

Source published

3 Jul 2026 21:16:59 UTC

Source modified

25 Oct 2026 15:10:00 UTC

Observed here

27 Oct 2026 07:23:38 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · 88ee5874-cf24-4952-aea0-31affedb7ff2 · Secondary · 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

### Summary Gitea fails to enforce OAuth2 access token scopes when the token is submitted via HTTP Basic authentication instead of a Bearer token. An OAuth2 application granted only `read:user` can use the same token as `Authorization: Basic base64(<token>:x-oauth-basic)` and perform write actions, including modifying profiles, adding email addresses, creating repositories, and deleting repositories as the authorizing user. ### Details **Root cause:** `services/auth/basic.go` accepts OAuth2 access tokens through the Basic auth path but does not store the token scope in the request context: ```go // services/auth/basic.go if uid != 0 { store.GetData()["LoginMethod"] = OAuth2TokenMethodName store.GetData()["IsApiToken"] = true // scope is NOT set return u, nil } ``` The scope enforcement middleware in `routers/api/v1/api.go` exits early when `ApiTokenScope` is absent: ```go // routers/api/v1/api.go — tokenRequiresScopes scope, scopeExists := ctx.Data["ApiTokenScope"].(auth_model.AccessTokenScope) if ctx.Data["IsApiToken"] != true || !scopeExists { return //<- exits without checking scope, all actions permitted } ``` When a token arrives via Bearer, `ApiTokenScope` is populated and scope checks apply normally. When the same token arrives via Basic auth, `ApiTokenScope` is never set, so `tokenRequiresScopes` returns immediately and no scope is enforced. **Suggested fix:** When an OAuth2 access token is accepted in `services/auth/basic.go`, populate `ApiTokenScope` in the request context identically to the Bearer-token OAuth2 path. ### PoC 1. Create an OAuth2 application in Gitea. 2. Authorize it as a normal user with scope `read:user` only. 3. Take the resulting access token and call a write endpoint both ways: **Bearer | correctly blocked:** ``` Authorization: Bearer <token> PATCH /api/v1/user/settings -> 403 Forbidden ``` **Basic | bypass:** ``` Authorization: Basic base64(<token>:x-oauth-basic) PATCH /api/v1/user/settings -> 200 OK ``` **All verified bypass endpoints using a `read:user`-only token:** | Endpoint | Bearer | Basic | |---|---|---| | `PATCH /api/v1/user/settings` | 403 | 200 | | `POST /api/v1/user/emails` | 403 | 200 | | `POST /api/v1/user/repos` | 403 | 200 | | `PATCH /api/v1/repos/{owner}/{repo}` | 403 | 200 | | `DELETE /api/v1/repos/{owner}/{repo}` | 403 | 200 | The bypass respects the user's normal repository permissions, it does not grant access to repositories the user cannot otherwise reach, and does not escalate to admin. ### Impact Any OAuth2 application with any restricted scope can silently operate beyond its granted permissions by switching from Bearer to Basic auth. An attacker who obtains a token (e.g. via a malicious OAuth2 app a user authorized) can: - Modify the victim's profile and settings - Add attacker-controlled email addresses to the victim's account - Create repositories as the victim - Modify or delete the victim's private repositories The entire OAuth2 scope system is effectively bypassed for any token submitted via Basic auth.

Source published

16 Jun 2026 23:40:34 UTC

Source modified

25 Jun 2026 19:56:25 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Publisher rating · HIGH

Gitea: OAuth2 access token scope enforcement bypass via HTTP Basic authentication in code.gitea.io/gitea

Source published

25 Jun 2026 18:43:19 UTC

Source modified

25 Jun 2026 19:45:30 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.