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Two newly disclosed vulnerabilities affect widely used JavaScript server components, with one enabling application-level denial of service in h3 and the other causing cross-client data exposure in mcp-handler. The h3 flaw, tracked as GHSA-Q5PR-72PQ-83V3, is an algorithmic complexity issue in chunked cookie processing that lets an attacker send a very small HTTP request and force disproportionate CPU consumption. Rated CVSS 7.5, the bug can starve event loops and degrade availability without requiring privileges or user interaction.
A separate issue in mcp-handler, tracked as GHSA-W2FM-25VW-VH7F, stems from a transport race condition that can leak sensitive MCP tool responses across client sessions. The vulnerability, rated CVSS 7.1, can expose database query results, local file contents, proprietary data, and raw large language model outputs, while also allowing limited attacker-controlled input injection when misrouted requests are processed in a victim session. The risk is highest in stateless serverless deployments such as AWS Lambda or edge runtimes where developers reuse global McpServer or StreamableHTTPServerTransport instances, while persistent Node.js deployments that create transport objects per connection are described as resistant to this specific flaw.
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2 events from the most recent confirmed update back to the earliest known activity.
A high-severity vulnerability in mcp-handler was disclosed involving a transport race condition that can leak sensitive data across client sessions. The flaw mainly impacts confidentiality, with stateless serverless deployments highlighted as especially vulnerable when global variable caching is used for shared transport or server instances.
A high-severity algorithmic complexity flaw in h3 was disclosed that can cause application-level denial of service by forcing disproportionate CPU consumption from a small HTTP request. The issue primarily affects availability and is especially risky in containerized and horizontally scaled environments where it can trigger crash loops and fleet-wide resource exhaustion.
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Researchers disclosed multiple security flaws affecting AWS MCP components, including a local file inclusion bug in the AWS Remote MCP Server and a critical command injection issue in `aws-mcp-server`. Varonis said authenticated users could abuse AWS CLI shorthand syntax, specifically the `@=` operator passed through the `aws___call_aws` tool, to read arbitrary files from the underlying host even when `FileAccessMode=NO_ACCESS` was enabled. AWS assigned **CVE-2026-4270** to the file access restriction bypass and said the issue was fixed in `aws-api-mcp-server` version **1.3.9**; the exposure affected the public endpoint `aws-mcp.us-east-1.api.aws` as well as self-hosted or forked deployments. A separate flaw, tracked as **CVE-2026-5058** and published by Trend Micro's Zero Day Initiative as **ZDI-26-246**, allows unauthenticated remote code execution in `aws-mcp-server` because user-supplied input in the allowed-commands list is not properly validated before being used in a system call. ZDI rated the bug **CVSS 9.8** and said successful exploitation lets attackers run arbitrary code in the MCP server context; the advisory was released as a 0-day after the vendor rejected the report. The disclosures landed alongside another AWS bulletin for **CVE-2026-4269**, an improper S3 ownership verification issue in the Bedrock AgentCore Starter Toolkit, underscoring broader security concerns around MCP-related tooling and the need for immediate patching and review of derivative implementations.
Jun 29, 2026
Two critical vulnerabilities were disclosed that allow **unauthenticated remote code execution** against exposed systems. `CVE-2024-40711` affects **Veeam Backup & Recovery** and stems from **deserialization of untrusted data**, enabling remote compromise when an attacker can deliver a crafted payload to a vulnerable instance. The flaw puts backup infrastructure at particular risk because successful exploitation could give attackers direct access to systems designed to store and manage recovery data. A separate flaw, `GHSA-V6WJ-C83F-V46X`, impacts the `domain_lookup` module in **`@profullstack/mcp-server`** and is described as an **OS command injection** vulnerability with a **CVSS 9.8** rating. Exploitation allows attackers to execute commands with the privileges of the Node.js process, exposing source code, configuration files, environment variables, database credentials, and cryptographic keys, while also enabling persistence, malware deployment, service termination, and broader lateral movement. Together, the disclosures highlight continued risk from internet-exposed enterprise software and developer tooling that process untrusted input without adequate safeguards.
Jun 29, 2026
Two newly disclosed web application flaws expose users to client-side data theft through content injection. In AVideo's **TopMenu** plugin, a stored cross-site scripting issue tracked as `GHSA-GMPC-FXG2-VCMQ` carries a CVSS 3.1 score of **6.1** and allows attackers to inject JavaScript that can read `document.cookie`, steal active session tokens, and impersonate users or administrators. Because the TopMenu component is rendered globally across the application, a malicious payload can execute for all site visitors, creating broad exposure and enabling follow-on attacks such as credential harvesting and fake login prompts. A separate issue in `rhukster/dom-sanitizer`, tracked as `GHSA-93VF-569F-22CQ`, allows **CSS injection** through SVG `style` tags and is rated **4.7** under CVSS 3.1. The flaw can be exploited remotely without authentication when a victim renders a crafted SVG in a browser, potentially disclosing the victim's IP address, browser details, exact page URL, and sensitive DOM-resident data such as CSRF tokens or partial session identifiers. While the sanitizer flaw does not directly alter server-side state or disrupt availability, both disclosures highlight how server-side handling of untrusted content can be turned into browser-based theft of session and application data.
Jun 29, 2026