high CVSS 7.5

CVE-2026-34824·Python vulnerability

Mesop is a Python-based UI framework that allows users to build web applications. From version 1.2.3 to before version 1.2.5, an uncontrolled resource consumption vulnerability exists in the WebSocket implementation of the Mesop framework. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of operating system threads. This leads to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS) for any application built on the framework. This issue has been patched in version 1.2.5.

Severity
high
Software
Python
Fixed in
1.2.5
Published
2026-04-03

Affected versions

From: 1.2.3

Until: 1.2.5

Fixed in: 1.2.5

How to fix this CVE

Upgrade the Mesop framework to version 1.2.5 or later to patch the WebSocket thread exhaustion vulnerability. Organizations running Mesop-based applications should prioritize this update to prevent denial-of-service attacks that exploit uncontrolled resource consumption in the WebSocket handler. Review your deployment pipeline to ensure Python dependencies are updated consistently across all environments.

sudo dnf update python3 python3-pip && pip3 install --upgrade mesop>=1.2.5

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /ws HTTP/1.1\nUpgrade: websocket.*Content-Length: \d{4,}.*Rapid successive frames at intervals <100ms or connection accept/close cycles >100/sec

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement WebSocket connection rate limiting (max 10 new connections per second per source IP), set per-connection message rate limits (max 100 frames/sec), enforce maximum frame payload size (limit to 1MB), and implement thread pool saturation alerts when worker threads exceed 80% utilization.

How to check if you are affected

  1. Check installed Mesop version: pip3 show mesop | grep Version
  2. Verify if your application imports or uses the Mesop framework: grep -r 'import mesop\|from mesop' /path/to/application
  3. Review WebSocket event logs for rapid connection spikes or repeated frame messages: grep -i 'websocket\|connection' /var/log/application.log | wc -l
  4. Confirm the patched version is active: pip3 show mesop | grep -E 'Version: 1.2.(5|[6-9]|[0-9]{2,})'

FAQ

What is CVE-2026-34824?

CVE-2026-34824 is a resource exhaustion vulnerability in Mesop's WebSocket implementation that allows unauthenticated attackers to trigger unbounded thread creation, leading to server denial of service through memory exhaustion.

Is CVE-2026-34824 being actively exploited?

No, this vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities catalog and has no publicly available exploit code, though the attack vector is straightforward.

What versions of the Mesop framework are affected by CVE-2026-34824?

Mesop versions 1.2.3 through 1.2.4 are vulnerable; version 1.2.5 and later include the patch.

How do I check if my server is vulnerable to CVE-2026-34824?

Run pip3 show mesop and check the Version field; if it shows 1.2.3 or 1.2.4, your installation is vulnerable. Upgrade immediately to 1.2.5 or later.

Does Defensia detect CVE-2026-34824?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Mesop is installed on a monitored server, CVE-2026-34824 will appear in your dashboard with remediation steps.

Related Python CVEs

CVE-2026-25632CVSS 10EPyT-Flow is a Python package designed for the easy generation of hydraulic and water quality scenario data of water distribution networks. Prior to 0.16.1, EPyT-Flow’s REST API parses attacker-controlled JSON request bodies using a custom deserializer (my_load_from_json) that supports a type field. When type is present, the deserializer dynamically imports an attacker-specified module/class and instantiates it with attacker-supplied arguments. This allows invoking dangerous classes such as subprocess.Popen, which can lead to OS command execution during JSON parsing. This also affects the loading of JSON files. This vulnerability is fixed in 0.16.1.
CVE-2026-28505CVSS 10Tautulli is a Python based monitoring and tracking tool for Plex Media Server. Prior to version 2.17.0, the str_eval() function in notification_handler.py implements a sandboxed eval() for notification text templates. The sandbox attempts to restrict callable names by inspecting code.co_names of the compiled code object. However, co_names only contains names from the outer code object. When a lambda expression is used, it creates a nested code object whose attribute accesses are stored in code.co_consts, NOT in code.co_names. The sandbox never inspects nested code objects. This issue has been patched in version 2.17.0.
CVE-2026-34938CVSS 10PraisonAI is a multi-agent teams system. Prior to version 1.5.90, execute_code() in praisonai-agents runs attacker-controlled Python inside a three-layer sandbox that can be fully bypassed by passing a str subclass with an overridden startswith() method to the _safe_getattr wrapper, achieving arbitrary OS command execution on the host. This issue has been patched in version 1.5.90.
CVE-2026-33054CVSS 10Mesop is a Python-based UI framework that allows users to build web applications. Versions 1.2.2 and below contain a Path Traversal vulnerability that allows any user supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation. This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds. This issue has been fixed in version 1.2.3.
CVE-2026-9135CVSS 9.9IBM Langflow OSS 1.0.0 through 1.10.0 Langflow versions up to 1.9.2 (commit 94981c443d4918517b9e8163d70fc598dc33a32d) contain a code injection vulnerability in the Policies component's ToolGuard integration that bypasses the allow_custom_components=false security control. The vulnerability exists because the validation mechanism only checks the main component source code in node_template["code"]["value"] but fails to validate dynamic CodeInput fields that store generated ToolGuard Python files. Attackers can embed malicious Python code in these unvalidated dynamic fields, which are persisted in Flow.data and later executed server-side when a guarded tool is invoked through the ToolGuard runtime. This allows authenticated users with flow creation privileges to achieve arbitrary Python code execution on the backend despite custom component restrictions. The vulnerability can be escalated through cross-tenant flow manipulation via the agentic MCP update_flow_component_field tool, which accepts attacker-controlled user_id parameters, enabling attackers to inject malicious code into victim users' flows. When combined with publicly accessible flows and specific misconfigurations (AUTO_LOGIN=true, NEW_USER_IS_ACTIVE=true), the attack can be conducted with reduced authentication requirements.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2026-34824. Free for 1 server.

Get started free