CVE-2026-56443

After PR #37118 / CVE-2026-25714
(fix: Unify public-only token filtering in API queries and repo access checks,
merged 2026-05-18, backport #37773 to 1.26.2, the May 2026 unification pass
for public-only token filtering, reporter Medoedus per the 1.26.2 release notes),
the public-only PAT scope is still bypassable on Repository and Package
scope categories when the owner's Visibility = Limited (instance-internal).

The sibling Org / User / ActivityPub cases in the same checkTokenPublicOnly
switch correctly reject Limited owners via !Visibility.IsPublic(). The
Repository / Package cases use repo.IsPrivate or Owner.Visibility.IsPrivate(),
both of which return false for VisibleTypeLimited, so a public-only PAT
strictly exceeds anonymous reach on a Limited owner.

Tested on gitea/gitea:1.26.2. The decisive marker is that PR #37118's
unification IS applied in the version under test (User-category PROBE returns
403 "token scope is limited to public users"). Despite that, the
Repository-category PROBE on the same Limited owner with the same PAT returns
200 and serves content.

Affected entry points (4 spots)

All four sinks check repo.IsPrivate or Owner.Visibility.IsPrivate() only.
VisibleTypeLimited falls through.

// modules/structs/visible_type.go
func (vt VisibleType) IsPrivate() bool { return vt == VisibleTypePrivate }   // line 39-40
func (vt VisibleType) IsLimited() bool { return vt == VisibleTypeLimited }   // line 33-34

Same-file evidence (routers/api/v1/api.go:246-299 after PR #37118)

case auth_model.AccessTokenScopeCategoryOrganization:
    orgPrivate := ... && !ctx.Org.Organization.Visibility.IsPublic()        // !IsPublic ✓
case auth_model.AccessTokenScopeCategoryUser:
    if ... && !ctx.ContextUser.Visibility.IsPublic() { ... }                // !IsPublic ✓
case auth_model.AccessTokenScopeCategoryActivityPub:
    if ... && !ctx.ContextUser.Visibility.IsPublic() { ... }                // !IsPublic ✓

case auth_model.AccessTokenScopeCategoryPackage:
    if ctx.Package != nil && ctx.Package.Owner.Visibility.IsPrivate() {     // IsPrivate ONLY ✗
        ctx.APIError(http.StatusForbidden, "token scope is limited to public packages")
        return
    }

TokenCanAccessRepo (services/context/api.go) reduces to !repo.IsPrivate:

// A public-only token cannot reach a private repo; any other token is unrestricted by this check.
func (ctx *APIContext) TokenCanAccessRepo(repo *repo_model.Repository) bool {
    return repo == nil || !ctx.PublicOnly || !repo.IsPrivate
}

CheckTokenScopes (services/context/permission.go:32):

if publicOnly && repo != nil && repo.IsPrivate {
    ctx.HTTPError(http.StatusForbidden)
    return
}

PoC (Docker e2e VERIFIED on gitea/gitea:1.26.2, 2026-06-05)

Full script in the report (run-poc.sh). Setup:

1. Create user limuser. PATCH /api/v1/admin/users/limuser with body
   {"visibility":"limited", ...}, response confirms "visibility":"limited".
2. Upload a generic package as limuser:
   PUT /api/packages/limuser/generic/secretpkg/1.0.0/secret.txt with body
   secret-content-internal-only → 201.
3. Create user attacker.
4. Mint PAT for attacker with scopes=["read:package","read:user","read:repository","public-only"].

Result on gitea/gitea:1.26.2, nine PROBEs:

PROBE A  (download package via attacker PAT)
    HTTP=200  Body: secret-content-internal-only

PROBE C  (read README of limuser's PUBLIC repo)
    HTTP=200  Body: {"name":"README.md", ...}

PROBE F  (sanity, User category, same PAT, same owner)
    HTTP=403  Body: {"message":"token scope is limited to public users"}

PROBE G  (Repository category, same PAT, same owner)
    HTTP=200  Body: {"name":"README.md", ...}                    ← bypass

PROBE H  (list limuser's repos, User category)
    HTTP=403  Body: {"message":"token scope is limited to public users"}

PROBE M  (git HTTPS smart protocol, info/refs)
    HTTP=200  Body: 001e# service=git-upload-pack ... HEAD ...   ← full clone enabled

PROBE N  (write attempt: POST contents/hacked.txt)
    HTTP=403  Body: {"message":"user should have a permission to write to the target branch"}
                                                                    Integrity:N confirmed

PROBE O  (Limited ORG, same bypass class)
    Org category    : HTTP=403  {"message":"token scope is limited to public orgs"}
    Repo category   : HTTP=200  README content                  ← bypass

Anonymous baseline (no auth) on every above endpoint: HTTP=401/404

Gitea's own server error string in PROBE F / H / O, "token scope is limited
to public users" / "public orgs", is the explicit declaration of intent.
Repository / Package category violates that intent on the same Limited owner.

Why this is not a duplicate of CVE-2026-25714

CVE-2026-25714 / PR #37118 (the May 2026 unification pass for public-only token
filtering, merged 2026-05-18, backported to 1.26.2 via PR #37773) realigned
checkTokenPublicOnly's Org / User / ActivityPub cases on !Visibility.IsPublic()
and introduced the TokenCanAccessRepo helper for the Repository / Issue /
Notification cases.

PROBE F on 1.26.2 returns 403 "token scope is limited to public users" for
the User category, i.e. PR #37118's unification IS in effect on the version
under test. The Repository / Package leak occurs after that fix; the Limited
gap is the next residual issue on the same hygiene effort (the Package case was
not touched, and TokenCanAccessRepo reduces to !repo.IsPrivate without
consulting owner visibility), not the same bug.

Suggested fix (4 spots, 1-line shape each)

// routers/api/v1/api.go:292  (checkTokenPublicOnly Package case)
- if ctx.Package != nil && ctx.Package.Owner.Visibility.IsPrivate() {
+ if ctx.Package != nil && !ctx.Package.Owner.Visibility.IsPublic() {

// routers/api/packages/api.go:76  (reqPackageAccess middleware)
- if ctx.Package != nil && ctx.Package.Owner.Visibility.IsPrivate() {
+ if ctx.Package != nil && !ctx.Package.Owner.Visibility.IsPublic() {

// services/context/api.go  (TokenCanAccessRepo helper)
- return repo == nil || !ctx.PublicOnly || !repo.IsPrivate
+ return repo == nil || !ctx.PublicOnly ||
+     (!repo.IsPrivate && repo.Owner != nil && repo.Owner.Visibility.IsPublic())

// services/context/permission.go:32  (CheckTokenScopes)
- if publicOnly && repo != nil && repo.IsPrivate {
+ if publicOnly && repo != nil &&
+     (repo.IsPrivate || (repo.Owner != nil && !repo.Owner.Visibility.IsPublic())) {

This aligns the Repository / Package categories with the User / Org / ActivityPub
siblings already shipped in PR #37118.

Reporter

JebeenLee