CVE-2026-44214

eventsource-encoder: SSE event injection via unsanitized event and id fields

State: Published
Severity: 5.8 Medium
Published: May 26, 2026
Updated: May 27, 2026
Reserved: May 5, 2026

Description

eventsource-encoder encodes events as well-formed EventSource/Server Sent Event (SSE) messages. Prior to 1.0.2, eventsource-encoder does not sanitize the event or id fields of an EventSourceMessage before serializing them. An attacker who controls either field can inject arbitrary Server-Sent Events line terminators (\n, \r, or \r\n) and thereby forge additional SSE fields or entire messages on the stream. This vulnerability is fixed in 1.0.2.

Scores

CVSS	Score	Vector	Source
3.1	5.8 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N	GitHub_M

Weaknesses

CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

Affected Products

Product	Versions
eventsource-encoderrexxars	< 1.0.2Affected

References

https://github.com/rexxars/eventsource-encoder/security/advisories/GHSA-m9g3-3g99-mhpx

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