What’s Vulnerable › Vulnerabilities

CVE-2026-44214: eventsource-encoder: SSE event injection via unsanitized event and id fields

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-26 · updated 2026-07-24
• Weakness: CWE-93

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.

Affected products

• rexxars eventsource-encoder: before 1.0.2 — fixed in 1.0.2

How to fix

Upgrade to a fixed version: rexxars eventsource-encoder 1.0.2. Check the vendor advisory for mitigations.

References

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

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