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CVE-2026-43968— CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1

Quick assessment

Affected
ninenines cowlib
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Cowlib是Nine Nines开源的一个Web协议消息解析与构建库。 cowlib 2.6.0版本存在注入漏洞，该漏洞源于cow_sse:event/1在cowlib中保护id和event字段免受 攻击但未保护裸 ，且内部prefix_lines/2函数仅按 分割，由于SSE规范要求解码器将 、 和 视为等效行终止符，控制任何这些字段的攻击者可注入额外SSE行并在接收端伪造具有任意事件类型和数据有效载荷的完整事件。

AI Predicted 7.5 Difficulty: Easy EPSS 0.46% · P39

Affected Version Matrix 2

VendorProduct Version RangeStatus
ninenines cowlib 2.6.0< 2.16.1 affected
93b2b897cde238506c803faad4d1602d79dba7c9< 6165fc40efa159ba1cceee7e7981e790acba5d9c affected
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I. Basic Information for CVE-2026-43968

Vulnerability Information
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Vulnerability Title
CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1
Source: CVE Program / CVE List V5
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对CRLF序列的转义处理不恰当(CRLF注入)
Source: CVE Program / CVE List V5
Vulnerability Title
Cowlib 注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cowlib是Nine Nines开源的一个Web协议消息解析与构建库。 cowlib 2.6.0版本存在注入漏洞，该漏洞源于cow_sse:event/1在cowlib中保护id和event字段免受 攻击但未保护裸 ，且内部prefix_lines/2函数仅按 分割，由于SSE规范要求解码器将 、 和 视为等效行终止符，控制任何这些字段的攻击者可注入额外SSE行并在接收端伪造具有任意事件类型和数据有效载荷的完整事件。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ninenines cowlib 2.6.0 ~ 2.16.1 cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*
ninenines cowlib 93b2b897cde238506c803faad4d1602d79dba7c9 ~ 6165fc40efa159ba1cceee7e7981e790acba5d9c cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-43968

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III. Intelligence Information for CVE-2026-43968

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Vendor Advisories for CVE-2026-43968 (2)

Same Patch Batch · ninenines · 2026-05-11 · 3 CVEs total

CVE-2026-43969 2.1 LOW Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1
CVE-2026-7790 Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS

IV. Related Vulnerabilities

Same product: cowlib
Same vendor: ninenines
Same weakness: CWE-93

V. Comments for CVE-2026-43968

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