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Researchers disclosed a remote code execution chain affecting default self-managed GitLab installations by exploiting two memory-safety flaws in the Ruby JSON parser Oj during Jupyter Notebook diff processing. The issue became reachable through GitLab’s handling of .ipynb files via the ipynbdiff component, allowing an authenticated user with permission to push commits and view diffs to upload crafted notebook files and execute arbitrary shell commands as the git user without administrator privileges or user interaction.
The exploit combined a one-byte memory overwrite with a heap information leak to bypass ASLR, corrupt parser state, and redirect execution to system(), aided by Puma thread reuse of the vulnerable parser instance. Researchers said successful compromise could expose source code, Rails secrets, service credentials, and internal services, creating opportunities for data theft, code tampering, and lateral movement. GitLab released fixes for CE/EE versions 18.10.8, 18.11.5, and 19.0.2, while Oj 3.17.3 patched the underlying library flaws; GitLab.com had already been updated before disclosure, and public proof-of-concept code has increased risk for unpatched deployments.
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6 events from the most recent confirmed update back to the earliest known activity.
Public proof-of-concept exploit code was released after disclosure, increasing the risk to unpatched self-managed GitLab deployments.
GitLab.com was already updated ahead of the public disclosure, reducing exposure for the hosted service before details of the exploit chain became public.
GitLab patched supported affected versions, including CE/EE releases 18.10.8, 18.11.5, and 19.0.2, to block exploitation of the Oj-based notebook diff attack path.
The Oj project fixed the underlying memory-safety issues in release 3.17.3, addressing the parser flaws used in the GitLab exploit chain.
Researchers disclosed an exploit chain that combines two memory corruption vulnerabilities in the Oj JSON parser to achieve remote code execution on default self-managed GitLab installations. The attack lets an authenticated user execute arbitrary shell commands as the git user without administrator privileges or user interaction.
The exploit path became reachable in GitLab 15.2.0 when Jupyter Notebook (.ipynb) files began being processed through the vulnerable Oj-based notebook diff functionality, enabling authenticated users with commit and diff-view permissions to target default self-managed installations.
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GitLab released security updates for Community Edition and Enterprise Edition in versions **16.6.1**, **16.5.3**, and **16.4.3**, urging affected self-managed installations to upgrade immediately. The fixes addressed multiple vulnerabilities spanning **XSS, privilege escalation, information disclosure, authorization bypass, package registry access issues, protected branch and pipeline schedule permission bypasses, and client-side denial of service**. The most severe issue was **`CVE-2023-6033`**, a high-severity cross-site scripting flaw in Jira integration configuration, while GitLab said **GitLab.com** was already running the patched version. One of the patched Enterprise Edition issues, **`CVE-2023-4658`**, was an incorrect authorization flaw that allowed a guest user to abuse the **"Allowed to merge"** permission when that right was inherited through a group. GitLab rated that bug **CVSS 3.1 / Low** and said it affected versions from **8.13 before 16.4.3**, **16.5 before 16.5.3**, and **16.6 before 16.6.1**. The release also included fixes for unauthorized access to release descriptions and other EE-specific authorization weaknesses, along with bundled component updates for **Mattermost**, **PostgreSQL**, and **pcre2**.
Jul 24, 2026
GitLab released security updates for **GitLab Community Edition (CE)** and **Enterprise Edition (EE)**, shipping patched versions **18.9.2**, **18.8.6**, and **18.7.6** to address multiple vulnerabilities affecting self-managed deployments. The Canadian Centre for Cyber Security issued advisory **AV26-222** urging organizations to review GitLab’s upstream advisory and apply the updates for any instances running versions prior to those releases. The update fixes **15 security issues**, including a high-severity **XSS** vulnerability (**CVE-2026-1090**, CVSS 8.7) in Markdown placeholder processing when the relevant feature flag is enabled, which could allow an authenticated attacker to inject malicious JavaScript into a victim’s browser. GitLab also addressed several **denial-of-service** conditions, including issues impacting the **GraphQL API** (resource exhaustion via recursion), repository archive endpoints, and JSON payload validation in the protected branches API; additional fixes include webhook-related DoS risks (e.g., **CVE-2025-13690**, **CVE-2025-12576**) and a **CRLF sequence** handling issue (**CVE-2026-3848**).
Jun 29, 2026
GitLab issued emergency security updates for self-managed Community Edition and Enterprise Edition instances to fix multiple high-severity vulnerabilities, including several cross-site scripting (**XSS**) flaws and unauthenticated denial-of-service (**DoS**) issues. The XSS bugs could allow attackers to run malicious JavaScript in users’ browsers, potentially leading to session hijacking, token theft, and repository manipulation, while the DoS flaws could disrupt CI/CD pipelines and broader workflow operations. The affected products are GitLab CE and EE versions earlier than `18.11.3`, `18.10.6`, and `18.9.7`, and administrators were urged to review GitLab’s release guidance and upgrade immediately to those patched versions. GitLab said its cloud-hosted platforms had already been remediated, while self-hosted operators were warned that single-node upgrades require downtime because of database migrations, whereas multi-node deployments can follow standard zero-downtime upgrade procedures.
Jun 29, 2026