CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1

6.3 / 10

MEDIUM

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

Description

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows SSE event splitting and injection via unvalidated field values.

cow_sse:event/1 in cowlib guards the id and event fields against \n but not against bare \r, and the internal prefix_lines/2 function used for data and comment fields splits only on \n. Because the SSE specification requires decoders to treat \r\n, \r, and \n as equivalent line terminators, an attacker who controls any of these fields can inject additional SSE lines and forge a complete event with an arbitrary event type and data payload on the receiving end. In typical deployments where browser EventSource clients or other SSE consumers dispatch on event.type and render event.data, this enables event splitting, client-side logic manipulation, and stored-XSS-equivalent behaviour when event data is inserted into the DOM.

This issue affects cowlib from 2.6.0.

Basic Information

ID CVE-2026-43968

Source EEF

Published May 11, 2026 at 18:06

Modified May 11, 2026 at 18:57

Affected Product

Vendor ninenines

Product cowlib

Version 2.6.0

Affected Versions ninenines cowlib 2.6.0
ninenines cowlib 93b2b897cde238506c803faad4d1602d79dba7c9

CWE Classification

CWE-93

References

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    "published": "2026-05-11T18:06:42.881Z",
    "modified": "2026-05-11T18:57:38.074Z",
    "type": "cve",
    "title": "CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1",
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CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1_CVE-2026-43968