CVE-2026-47427

GitHub MCP Server: Nil Pointer Dereference DoS in completion/complete Handler

GitHub MCP Server is GitHub's official MCP Server. Prior to 1.1.0, the CompletionsHandler function in pkg/github/server.go accesses params.Ref without first checking whether it is nil, so a completion/complete request with a missing or empty ref field triggers a nil pointer dereference and a Go runtime panic; because the crash occurs before any authentication or token validation, any unauthenticated client able to send JSON-RPC messages can crash the server, resulting in a complete denial of service. This issue is fixed in version 1.1.0.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Github

Products

Github-mcp-server Mcp Server

CVE-2026-54163

secure_headers: CSP directive injection via sandbox, plugin_types, and report_to when given untrusted input

secure_headers manages application of security headers with many safe defaults. Prior to 7.3.0, secure_headers builds the Content-Security-Policy value by stitching directives with ; separators, and build_sandbox_list_directive, build_media_type_list_directive, and build_report_to_directive interpolate caller-supplied strings without scrubbing ;, \r, or \n. When untrusted input reaches SecureHeaders.override_content_security_policy_directives or append APIs for :sandbox, :plugin_types, or :report_to, an attacker can inject a CSP directive such as script-src 'unsafe-inline' * before the legitimate script-src, enabling XSS reachability through these sinks or CSP report exfiltration. This issue is fixed in version 7.3.0.

CVSS 3.1 · 4.7 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Secure Headers

CVE-2026-15007

Denial of service vulnerability in GitHub Enterprise Server allowed service disruption via deeply nested YAML in release notes configuration

A denial of service vulnerability was identified in GitHub Enterprise Server that allowed an authenticated user to cause service disruption by supplying a repository release notes configuration file containing deeply nested YAML. When release notes were generated, the configuration file was parsed without a nesting depth limit, causing excessive resource consumption that could render the instance unresponsive. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.18, 3.18.12, 3.19.9, 3.20.5, and 3.21.3. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 5.7 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-15783

Missing Authorization vulnerability was identified in GitHub Enterprise Server that allowed reading private repository metadata via delegated bypass rule suites

A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed an authenticated user with write access to any repository to read metadata from private repositories they did not have access to, including private repository owners and names, branch names, commit SHAs, commit messages, and the pushing actor. The delegated bypass endpoint resolved a rule suite directly from an attacker-supplied, encoded identifier without verifying that the requesting user could read the rule suite's repository, and because these identifiers are sequential an attacker could enumerate them across the instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.18, 3.18.12, 3.19.9, 3.20.5, and 3.21.3. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-14340

An incorrect authorization vulnerability in GitHub Enterprise Server allows issue creation in unrelated public repositories

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed a user-to-server token scoped to a GitHub App installation to perform certain write operations on public repositories outside the token's intended scope. This was possible because the authorization check only verified that the installation had read permissions on the target repository rather than verifying that the token's installation was explicitly granted access to that repository. An attacker who obtained a victim's user-to-server token could create issues, issue comments, commit comments, and private vulnerability reports on any public repository, appearing as the victim user with no indication of the app involvement. This vulnerability was fixed by adding a repository scope check for user-to-server tokens issued by global apps. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.2, 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-9132

Missing authorization vulnerability in GitHub Enterprise Server allowed disclosure of private repository contents via the Copilot pull request diff summary endpoint

A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed an authenticated user to read source code from private repositories they did not have access to. The Copilot pull request description diff summary endpoint accepted a cross-repository comparison range and rendered the resulting diff without verifying that the requesting user was authorized to view the target repository. Exploitation required an authenticated account on the instance with read access to at least one repository to use as the comparison base. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.17.17, 3.18.11, 3.19.8, and 3.20.4. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 6 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-9106

UI misrepresentation vulnerability in GitHub Enterprise Server allowed unauthorized organization runner management via undisclosed OAuth scope on consent screen

A UI misrepresentation vulnerability was identified in GitHub Enterprise Server that allowed an OAuth application to gain unintended access to an organization's runner management. An attacker could exploit this by creating an OAuth application requesting the manage_runners:org scope and directing a victim user to authorize it, as the scope was not displayed on the authorization consent screen. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.2, 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 4.8 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-10585

Stored cross-site scripting vulnerability in GitHub Enterprise Server allowed arbitrary JavaScript execution via crafted Discussion titles in the Q&A category

A stored cross-site scripting vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to execute arbitrary JavaScript in another user's browser by injecting a crafted payload into the title of a Discussion in the Q&A category. The AnsweredQuestionStructuredDataComponent did not escape user-controlled Discussion titles before embedding them in a <script type="application/ld+json"> block, allowing the title to break out of the script context. The injection was escalated to a full cross-site scripting attack on GitHub Enterprise Server by leveraging JSONP callback support in the REST API to bypass the Content Security Policy. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-9312

Server-Side Request Forgery vulnerability in GitHub Enterprise Server allowed access to internal services via path traversal in upload endpoint

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to send crafted requests to internal services by exploiting insufficient input validation in an upload endpoint. By injecting path traversal content into request parameters, an attacker could bypass the intended request flow and redirect internal API calls, potentially accessing internal services and exposing sensitive credentials. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.17, 3.18.11, 3.19.8, 3.20.4, and 3.21.2. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 9.2 Critical EPSS 9.2% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-48529

GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion

GitHub MCP Server is GitHub's official MCP Server. From 0.22.0 until 1.1.2, when running in HTTP mode with --lockdown-mode enabled, the RepoAccessCache is implemented as a process-global singleton initialized with the first authenticated user's GraphQL client. All subsequent requests from different users share this singleton and their lockdown-related GraphQL queries are executed using the first user's credentials. The singleton is never updated to reflect later users' tokens. This vulnerability is fixed in 1.1.2.

CVSS 3.1 · 6 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Github-mcp-server

CVE-2024-1359

Command injection vulnerability was identified in GitHub Enterprise Server that allowed privilege escalation in the Mangement Console

A command injection vulnerability was identified in GitHub Enterprise Server that allowed an attacker with an editor role in the Management Console to gain admin SSH access to the appliance when setting up an HTTP proxy. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and access to the Management Console with the editor role. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12 and was fixed in versions 3.11.5, 3.10.7, 3.9.10, and 3.8.15. This vulnerability was reported via the GitHub Bug Bounty program https://bounty.github.com .

CVSS 3.1 · 9.1 Critical EPSS 2.3% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2022-46255

Improper Limitation of a Pathname to a Restricted Directory in GitHub Enterprise Server leading to RCE

An improper limitation of a pathname to a restricted directory vulnerability was identified in GitHub Enterprise Server that enabled remote code execution. A check was added within Pages to ensure the working directory is clean before unpacking new content to prevent an arbitrary file overwrite bug. This vulnerability affected only version 3.7.0 of GitHub Enterprise Server and was fixed in version 3.7.1. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 3.1 · 9.8 Critical EPSS 1.6% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-4821

Proxy configuration command injection vulnerability found in GitHub Enterprise Server Management Console configuration API

This CVE ID has been rejected or withdrawn by its CVE Numbering Authority as it was published in error.

CVSS n/a EPSS n/a KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-48501

GitHub CLI tokens leak via `gh attestation` commands

GitHub CLI (gh) is GitHub’s official command line tool. Prior to 2.93.0, GitHub CLI incorrectly includes authorization header in API requests to TUF repository mirrors via gh attestation, gh release verify, and gh release verify-asset commands. The CLI uses a shared HTTP client with an authentication layer that automatically attaches tokens to outgoing requests. This layer lacks accurate host detection and can incorrectly attribute the target host, providing it with a token it should never receive. Specifically, the host normalization logic collapses any *.github.com subdomain to github.com, so a request to tuf-repo.github.com (a GitHub Pages site, not a GitHub API endpoint) is treated as a request to github.com and receives the user's github.com token. For hosts that don't match github.com or a known GHES instance at all, the resolver falls back to GH_ENTERPRISE_TOKEN if set. The gh attestation, gh release verify and gh release verify-asset commands fetch data from several external hosts as part of their normal operation (TUF metadata from tuf-repo.github.com and tuf-repo-cdn.sigstore.dev, artifact bundles from Azure Blob Storage). Because these requests go through the same authenticated HTTP client, the token is sent to all of them. This vulnerability is fixed in 2.93.0.

CVSS 3.1 · 7.4 High EPSS < 1% KEV · Not listed

Vendors

Cli Github

Products

Cli Cli

CVE-2026-8606

Server-Side Request Forgery in GitHub Enterprise Server via Advisory Package URL Endpoint

A Server-Side Request Forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to cause the server to issue HTTP requests to internal services via the security advisories package lookup feature. By directing requests to an internal management service and measuring response timing, an attacker could infer the values of sensitive environment variables, including signing secrets and private keys. Exploitation required GitHub Packages to be enabled; on instances not running in private mode the vulnerability was exploitable without authentication, otherwise any authenticated user could exploit it. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21.1 and was fixed in versions 3.20.3, 3.19.7, 3.18.10, 3.17.16, and 3.16.19. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 7 High EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-45803

gh: GitHub Actions log output in `gh run view` allows terminal escape sequence injection

`gh` is GitHub’s official command line tool. From 1.6.0 to before 2.92.0, a security vulnerability has been identified in GitHub CLI that could allow terminal escape sequence injection when users view GitHub Actions workflow logs using gh run view --log or gh run view --log-failed. The vulnerability stems from the way GitHub CLI handles raw Actions log output. The gh run view --log and gh run view --log-failed commands stream workflow log lines to stdout or the configured pager without sanitizing terminal control sequences. An attacker who can influence GitHub Actions log content, for example via a PR triggered workflow, can embed escape sequences that are replayed in the user's terminal when they inspect the run. Depending on the victim's terminal emulator, injected sequences could change the window title, manipulate on screen content, or in some terminal emulators (such as screen) potentially execute arbitrary commands. This vulnerability is fixed in 2.92.0.

CVSS 3.1 · 3.5 Low EPSS < 1% KEV · Not listed

Vendors

Cli Github

Products

Cli Cli

CVE-2026-6736

Authentication bypass vulnerability in GitHub Enterprise Server allowed creation of local user accounts bypassing the configured external identity provider

An authentication bypass vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to create a local user account, bypassing the configured external identity provider. When external authentication was enabled, the signup endpoint did not properly enforce the authentication restriction, allowing account creation and session establishment without identity provider validation. The created account was limited to the default base permissions configured on the instance. Exploitation required network access to a GHES instance configured with an external authentication provider. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18.

CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-7541

Denial of service vulnerability in GitHub Enterprise Server allowed service disruption via unauthenticated API endpoint

A denial of service vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to cause service disruption by sending crafted requests with deeply nested JSON payloads to an unauthenticated API endpoint. The endpoint parsed user-controlled JSON request bodies without size or depth limits, causing excessive CPU and memory consumption. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-8034

Server-side request forgery vulnerability in GitHub Enterprise Server notebook viewer via URL parser confusion

A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 7.9 High EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server

CVE-2026-8106

Reflected HTML injection vulnerability in GitHub Enterprise Server Management Console login page allowed credential theft

A reflected HTML injection vulnerability was identified in the GitHub Enterprise Server Management Console login page that could allow credential theft. The redirect_to query parameter on the /setup/unlock endpoint was reflected into an HTML attribute without proper sanitization, enabling an attacker to inject a form element that could capture administrator credentials. Exploitation required an administrator to click a crafted link and enter their credentials. This vulnerability affected GitHub Enterprise Server versions 3.19.1 through 3.19.5 and 3.20.0 through 3.20.1, and was fixed in versions 3.19.6 and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS 4.0 · 5.9 Medium EPSS < 1% KEV · Not listed

Vendors

Github

Products

Enterprise Server