What is CVE-2026-44217?

CVE-2026-44217 is a medium-severity security vulnerability in sse-channel (npm), affecting versions <= 4.0.0. It is fixed in 4.0.1.

Which versions of sse-channel are affected by CVE-2026-44217?

sse-channel (npm) versions <= 4.0.0 is affected.

Is there a fix for CVE-2026-44217?

Yes. CVE-2026-44217 is fixed in 4.0.1. Upgrade to this version or later.

Is CVE-2026-44217 exploitable, and should I be worried?

Whether CVE-2026-44217 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.

What actually determines whether CVE-2026-44217 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-2026-44217?

Upgrade sse-channel to 4.0.1 or later.

CVE-2026-44217 in sse-channel

Q: Which versions of sse-channel are affected by CVE-2026-44217?

sse-channel (npm) versions <= 4.0.0 is affected.

Q: Is there a fix for CVE-2026-44217?

Yes. CVE-2026-44217 is fixed in 4.0.1. Upgrade to this version or later.

Q: Is CVE-2026-44217 exploitable, and should I be worried?

Whether CVE-2026-44217 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.

Q: What actually determines whether CVE-2026-44217 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.

Q: How do I fix CVE-2026-44217?

Upgrade sse-channel to 4.0.1 or later.

Summary

sse-channel: SSE Injection via unsanitized event fields

Workarounds

Do not allow user data to control event, retry or id fields, and if you must - sanitize the input before passing it to sse-channel, stripping any newlines.

Resources

https://github.com/rexxars/sse-channel/issues/42

Impact

Implementations that allows user-provided values to be passed to event, retry or id fields would be susceptible to event spoofing, where an attacker could inject arbitrary messages into the stream.

Event Spoofing: Attacker can inject arbitrary SSE events into the stream
Client-side Manipulation: Injected events can trigger unintended behavior in frontend JavaScript EventSource listeners
Data Integrity: Consumers of the SSE stream cannot distinguish injected events from legitimate ones

Affected versions

sse-channel (<= 4.0.0)

Security releases

sse-channel → 4.0.1 (npm)

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.

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Remediation advice

Patch available in v4.0.1.

Frequently Asked Questions

What is CVE-2026-44217? CVE-2026-44217 is a medium-severity security vulnerability in sse-channel (npm), affecting versions <= 4.0.0. It is fixed in 4.0.1.
Which versions of sse-channel are affected by CVE-2026-44217? sse-channel (npm) versions <= 4.0.0 is affected.
Is there a fix for CVE-2026-44217? Yes. CVE-2026-44217 is fixed in 4.0.1. Upgrade to this version or later.
Is CVE-2026-44217 exploitable, and should I be worried? Whether CVE-2026-44217 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-2026-44217 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-2026-44217? Upgrade sse-channel to 4.0.1 or later.