Summary
socket.io allows an unbounded number of binary attachments
Workarounds
There is no known workaround except upgrading to a safe version.
For more information
If you have any questions or comments about this advisory:
- Open a discussion here
Impact
A specially crafted Socket.IO packet can make the server wait for a large number of binary attachments and buffer them, which can be exploited to make the server run out of memory.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
| Version range | Used by | Fixed version |
|---|---|---|
>=4.0.0 <4.2.6 |
[email protected] and [email protected] |
4.2.6 |
>=3.4.0 <3.4.4 |
[email protected] |
3.4.4 |
<3.3.5 |
[email protected] |
3.3.5 |
Frequently Asked Questions
- What is CVE-2026-33151? CVE-2026-33151 is a high-severity security vulnerability in socket.io-parser (npm), affecting versions < 3.3.5. It is fixed in 3.3.5, 3.4.4, 4.2.6.
- Which versions of socket.io-parser are affected by CVE-2026-33151? socket.io-parser (npm) versions < 3.3.5 is affected.
- Is there a fix for CVE-2026-33151? Yes. CVE-2026-33151 is fixed in 3.3.5, 3.4.4, 4.2.6. Upgrade to this version or later.
- Is CVE-2026-33151 exploitable, and should I be worried? Whether CVE-2026-33151 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33151 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33151?
- Upgrade
socket.io-parserto 3.3.5 or later - Upgrade
socket.io-parserto 3.4.4 or later - Upgrade
socket.io-parserto 4.2.6 or later
- Upgrade