Vulnerability 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 before 2.16.1.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Ninenines | Cowlib | >= 2.6.0, < 2.16.1 |
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-43968.htmlVendor Advisory
- https://github.com/ninenines/cowlib/commit/6165fc40efa159ba1cceee7e7981e790acba5Patch
- https://osv.dev/vulnerability/EEF-CVE-2026-43968Third Party Advisory
FAQ
What is CVE-2026-43968?
CVE-2026-43968 is a vulnerability with a CVSS score of 4.0 (MEDIUM). 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 ...
How severe is CVE-2026-43968?
CVE-2026-43968 has been rated MEDIUM with a CVSS base score of 4.0/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-43968?
Check the references section above for vendor advisories and patch information. Affected products include: Ninenines Cowlib.