sse-channel: SSE Injection via unsanitized event fields
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
Patches
Patch available in v4.0.1.
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
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | sse-channel | < 4.0.1 | 4.0.1 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-93- Platform
- npm
- Package
sse-channel- Disclosed
- 05.05.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-84hm-wfh8-c5pg - CC BY 4.0
Vulnerability history: sse-channel
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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