dbcve.org
AsyncuaApplication · Asyncua Project

CVE-2022-25304

HIGH · 7.5 CVSS v3.1 Published 2022-08-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
All versions of package opcua; all versions of package asyncua are vulnerable to Denial of Service (DoS) due to a missing limitation on the number of received chunks - per single session or in total for all concurrent sessions. An attacker can exploit this vulnerability by sending an unlimited number of huge chunks (e.g. 2GB each) without sending the Final closing chunk.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The opcua and asyncua Python libraries fail to limit the number or size of OPC UA message chunks received during a session. An attacker can send unlimited huge chunks (up to 2GB each) without sending the required Final closing chunk, causing memory exhaustion and DoS due to unbounded buffer allocation.

MitigationImplement and enforce limits on: (1) maximum chunks per session, (2) maximum chunks across all concurrent sessions, (3) maximum total memory per session, and (4) timeouts for incomplete messages. Add connection throttling and monitoring.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AsyncuaApplication
Affected:all versions
OpcuaApplication
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if asyncua or opcua Python libraries are installed
    Run 'pip list' or check your requirements.txt for packages named 'asyncua' or 'opcua'. Also check for any fork or derivative packages.
    Affected if Either asyncua or opcua package is present in your Python environment
  2. Confirm the OPC UA service network exposure
    Review your firewall rules, network configuration, and service bindings. Determine if the OPC UA port (typically 4840) is accessible from untrusted networks or the public internet.
    Affected if The OPC UA service port is open to untrusted or external network segments
  3. Check if the OPC UA service handles external/untrusted clients
    Review your OPC UA server configuration and application logic to determine if connections from external systems, third-party clients, or non-vpn users are accepted.
    Affected if The OPC UA server accepts connections from untrusted or anonymous clients
  4. Verify if message chunk limits are externally enforced
    Inspect any proxy, load balancer, WAF, or network-level controls that may limit OPC UA chunk sizes or total message memory allocation. Check if these limits are configured and active.
    Affected if No network-level chunk or memory limits are enforced between the client and server
  5. Check for application-level rate limiting or chunk throttling
    Review your application code or middleware for any implementation that limits chunks per session, max chunk size, or memory allocation per connection.
    Affected if No application-level limits on chunk count, chunk size, or memory usage are implemented

You are affected if you have asyncua or opcua libraries running and your OPC UA service accepts connections from untrusted clients without network or application-level chunk/memory limits in place.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement and enforce limits on: (1) maximum chunks per session, (2) maximum chunks across all concurrent sessions, (3) maximum total memory per session, and (4) timeouts for incomplete messages. Add connection throttling and monitoring.

Fix this in Asyncua Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,600
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,960.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2022-25304 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2022-25304 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data