CVE-2026-12664: 
GitLab 脆弱性分析と緩和策

CVE-2026-12664 is an authorization bypass vulnerability in GitLab CE/EE caused by insufficient scope enforcement on a GraphQL field. It affects all versions from 18.2 through 19.3.5, 19.4.0 through 19.4.2, and 19.5.0, for both Community and Enterprise editions. Under certain conditions, an authenticated user holding a read_api-scoped token can retrieve a project's incoming email address and create work items — operations that should require higher-privilege tokens. The vulnerability was published on October 22, 2026, and carries a CVSS v3.1 base score of 6.8 (Medium) (Feedly, EUVD).

The root cause is classified as CWE-863 (Incorrect Authorization): the GitLab GraphQL API fails to properly enforce token scope restrictions on at least one field, allowing a read_api-scoped token to perform write operations (work item creation) and access sensitive project metadata (incoming email address) that should be gated behind higher-privilege scopes. Exploitation requires an authenticated session with a valid read_api-scoped personal access token and specific, unspecified conditions to be met, making the attack complexity high. The vulnerability was originally reported via HackerOne (report #3735499) and tracked internally at GitLab work item #603510 (Feedly, GitLab Issue).

Successful exploitation allows an attacker to bypass the intended restrictions of a read_api-scoped token, achieving both confidentiality impact (retrieving a project's incoming email address, which could be leveraged for email-based project interactions or phishing) and integrity impact (creating unauthorized work items within a project). While availability is not affected, the combination of high confidentiality and integrity impact on project data represents a meaningful risk for organizations relying on GitLab's token scoping model for least-privilege access control (Feedly, EUVD).

As of the time of disclosure, there is no public proof-of-concept exploit and no evidence of in-the-wild exploitation (Feedly). The NVD SSVC assessment classifies exploitation as "none" and the attack as non-automatable, reflecting the high attack complexity and specific preconditions required. The EPSS score is approximately 0.0025 (0.25%), indicating a low near-term probability of exploitation. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (Feedly, EUVD).

1. Obtain a read_api-scoped token: The attacker must already be authenticated to the GitLab instance and possess (or have obtained) a personal access token scoped to read_api only.
2. Identify a target project: Enumerate accessible GitLab projects using the read_api token via standard GitLab REST or GraphQL API calls.
3. Query the vulnerable GraphQL field: Craft a GraphQL query targeting the field that exposes the project's incoming email address, which should normally be restricted to higher-privilege scopes. Submit this query using the read_api token.
4. Retrieve the incoming email address: Under the specific conditions that trigger the insufficient scope enforcement, the API returns the project's incoming email address, which can be used for further reconnaissance or abuse (e.g., sending emails to create issues via email).
5. Create unauthorized work items: Exploit the same scope enforcement gap to submit GraphQL mutations that create work items (issues/tasks) within the target project, an operation that should require write-level token permissions (Feedly, GitLab Issue).

• Logs: GitLab application logs showing GraphQL requests from read_api-scoped tokens that access project incoming email fields or execute work item creation mutations; audit log entries for work item creation events attributed to tokens that should only have read access.
• Network: Unusual GraphQL POST requests to /api/graphql from authenticated sessions using read_api tokens that include mutation operations or queries for incomingEmail-related fields.
• Application: Unexpected work items (issues, tasks) appearing in projects without corresponding user activity from accounts with appropriate write permissions; review of token audit logs for read_api tokens performing write-equivalent actions (Feedly).

GitLab has released patched versions: 19.3.6, 19.4.3, and 19.5.1. All GitLab CE/EE administrators running versions from 18.2 onward should upgrade to one of these fixed releases immediately. As a supplementary measure, administrators should audit existing read_api-scoped personal access tokens, consider regenerating them post-upgrade, and review recent work item creation activity and project data access logs for any anomalous behavior from read_api tokens (GitLab Patch Release, Feedly).

The vulnerability received coverage from several security news outlets including SecurityOnline, GBHackers, CyberSecurityNews, Heise, and TheCyberThrone, largely in the context of GitLab's broader October 2026 patch release that also addressed a critical RCE vulnerability (Heise). Community discussion on Mastodon/InfoSec.exchange noted the patch release. Detection plugins were published by Tenable (Nessus plugin 370160) shortly after disclosure, indicating prompt response from the security tooling community (Feedly).