sse-channel CVE-2026-44217
MEDIUM
GHSA-84hm-wfh8-c5pg
CVSS VectorNVD
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionNVD
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
https://github.com/rexxars/sse-channel/issues/42
AnalysisAI
Event spoofing in sse-channel (npm) allows attackers to inject arbitrary Server-Sent Events (SSE) messages by passing unsanitized user input to the event, retry, or id fields, enabling client-side manipulation and data integrity violations. Affects sse-channel versions 4.0.0 and earlier; patched in v4.0.1. …
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External POC / Exploit Code
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