{"id":"CVE-2026-27761","aliases":["GHSA-3pww-vcvm-3gmj","GO-2026-6031"],"url":"https://o3.security/vulnerability/CVE-2026-27761","summary":"Gitea repository feeds bypass API token scope enforcement","details":"### Summary\nA Gitea personal access token (PAT) restricted to a non-repository scope (e.g. `read:issue`) can read the commit history of any private repository the token owner can access, via the repository RSS/Atom feed endpoints. The same token is correctly denied (403) on `/raw`, `/media`, `/archive`, and the contents API. It leaks commit SHAs, full commit messages (which frequently contain secrets and internal context), and committer name + email.\n\n### Details\nGitea enforces PAT scope on repository-content endpoints via `checkDownloadTokenScope()` (added in PR #37698, extended to the archive endpoint by the CVE-2026-20706 fix in 1.26.2). The RSS/Atom feed handlers were never included: they (a) opt into PAT auth via `webAuth.AllowBasic`, (b) serve private-repo content, but (c) never call `checkDownloadTokenScope()`.\n\nAffected handlers (all carry `AllowBasic`, none call the scope check):\n- `RenderBranchFeedRSS/Atom` - `routers/web/feed/render.go` (last 10 commits: SHA, title, full message, committer name + email)\n- `ShowFileFeed` - `routers/web/feed/file.go` (per-file commit history)\n- repo activity feed `/{owner}/{repo}.rss` / `.atom`\n- `TagsListFeedRSS/Atom`, `ReleasesFeedRSS/Atom` - `routers/web/repo/release.go`\n\nRoot cause: `routers/web/web.go` registers the feed routes with `webAuth.AllowBasic` so a PAT authenticates, but the unit-permission middleware only checks the user's access, not the token's scope. `checkDownloadTokenScope` (`routers/web/repo/download.go` and the archive `Download` in `repo.go`) exists to close exactly that gap and is absent from the feed handlers. Same class as the recently fixed download/archive bypasses (GHSA-cr4g-f395-h25h / CVE-2026-20706); the feeds are the surface those fixes missed.\n\n### PoC\nTested on `gitea/gitea:1.26.2-rootless`, confirmed present at `main` HEAD (9608cc2, 2026-06-13).\n1. User `carol` owns private repo `carol/priv` with a commit (message: \"add confidential secret\").\n2. Create a PAT scoped to issues only, no repository scope:\n   `curl -u carol:PASS -X POST $HOST/api/v1/users/carol/tokens -d '{\"name\":\"t\",\"scopes\":[\"read:issue\"]}'`\n3. Scope-enforcing sibling correctly denies it:\n   `curl -u carol:$TOK $HOST/carol/priv/raw/branch/main/secret.txt`  ->  403\n4. The feed leaks private data with the same token:\n   `curl -u carol:$TOK $HOST/carol/priv/rss/branch/main`  ->  200, returns\n   `<description>add confidential secret ... this commit message itself is sensitive</description>`\n\n| Auth (same read:issue token) | /raw/branch/main/secret.txt | /rss/branch/main |\n|---|---|---|\n| anonymous | - | 404 (private repo hidden) |\n| invalid token | - | 401 |\n| read:issue token (no repo scope) | 403 (scope enforced) | 200 + private commit data |\n| full-scope token | 200 | 200 (legitimate) |\n\n### Impact\nPATs are routinely issued narrowly and handed to third-party bots, CI jobs, or chat integrations that are meant to have no code access. This bypass lets such a token exfiltrate private-repository commit history (messages often hold secrets, ticket refs, internal context) and committer emails for every repository the owner can read. Confidentiality only; no integrity or availability impact. Preconditions: a valid PAT of any non-repository scope owned by a user with read access to the target private repo, and feeds enabled (`Other.EnableFeed`, default ON).\n\nSuggested fix: call `checkDownloadTokenScope(ctx)` at the start of each feed handler (mirroring `download.go`). Longer-term, enforce repository token scope in a single route-group middleware wherever `AllowBasic` / `AllowOAuth2` is set on a repo-content route, so the next added endpoint cannot miss it.","published":"2026-07-03T20:19:36.576Z","modified":"2026-10-28T02:31:07.498623183Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"},"epss":{"score":0.00367,"percentile":0.30398,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"code.gitea.io/gitea","fixedVersion":"1.26.3"}],"fix":{"url":"https://github.com/go-gitea/gitea/pull/38147","label":"go-gitea/gitea#38147"},"references":[{"type":"ADVISORY","url":"https://blog.gitea.com/release-of-1.26.3-and-1.26.4/"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27761.json"},{"type":"ADVISORY","url":"https://github.com/go-gitea/gitea/releases/tag/v1.26.3"},{"type":"ADVISORY","url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-3pww-vcvm-3gmj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27761"},{"type":"FIX","url":"https://github.com/go-gitea/gitea/pull/38147"},{"type":"WEB","url":"https://github.com/go-gitea/gitea/commit/9e84deb969aff5c1115c2984e41250f28c78451f"},{"type":"WEB","url":"https://blog.gitea.com/release-of-1.26.3-and-1.26.4"},{"type":"PACKAGE","url":"https://github.com/go-gitea/gitea"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:31:07.498623183Z"}}