CVE-2026-43968
MediumCVSS 4.0Exploitation Probability (EPSS)
Low risk18th percentile - higher than 18% of all known CVEs
Summary
cowlib versions 2.6.0 to before 2.16.1 contain a CRLF injection vulnerability allowing SSE event splitting and injection via unvalidated field values. An attacker can inject additional SSE lines and forge a complete event with arbitrary type and data.
Risk Assessment
This may lead to client-side logic manipulation and stored-XSS-equivalent behavior when event data is inserted into the DOM.
Recommendation
Update cowlib to version 2.16.1 or later.
Other vulnerabilities in cowlib
See all- CVE-2026-43971Medium
cowlib (Erlang) versions 2.9.0 through 2.20.0 fail to escape values inserted into the Link: header in cow_link:link/1. Special characters in the URI, rel, or attribute keys can be injected into the header, allowing additional Link directives to be smuggled. As a result, victim browsers may be forced to make connections to attacker-controlled resources.
- CVE-2026-59248High
A vulnerability in the cowlib library allows an unauthenticated remote attacker to exhaust memory on a vulnerable server or client by sending specially crafted HTTP/2 or HTTP/3 frames. The issue stems from missing limits in the HPACK and QPACK decoder, which processes arbitrarily long prefixed integers, causing large bignum allocations and heavy garbage collection churn.
- CVE-2026-43966Medium
A vulnerability in the cowlib library (from version 2.9.0 onward) involves improper neutralization of CRLF sequences in HTTP headers, enabling HTTP response splitting attacks. The cow_http_struct_hd:escape_string/2 function in cowlib only escapes \ and ", passing all other bytes through verbatim, creating an encoder/decoder asymmetry. An attacker can inject \r\n into the serialized header, allowing new headers to be added and potentially splitting the HTTP response.
- CVE-2026-43970High
CVE-2026-43970 is a vulnerability related to improper handling of highly compressed data in the cowlib library, which can lead to remote denial of service attacks via memory exhaustion. It allows unauthenticated users to send specially crafted SPDY frames that can cause significant memory consumption.
- CVE-2026-43969Low
The cowlib Erlang library's cow_cookie:cookie/1 function builds a Cookie header without validating cookie names or values. This allows injection of ;, comma, CR, LF, or TAB characters, enabling cookie smuggling and HTTP request splitting. Affects versions from 2.9.0 before 2.21.0.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS