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CVE-2026-43969— Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/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 2.9.0版本存在注入漏洞，该漏洞源于cow_cookie:cookie/1在cowlib中从名称值对列表构建客户端Cookie请求标头而未验证任一字段，控制cookie名称或值的攻击者可向序列化标头注入;、、、CR、LF或TAB字符，实现cookie走私和HTTP请求标头分割攻击。

CVSS 2.1 · Low EPSS 0.14% · P4

Affected Version Matrix 2

VendorProduct Version RangeStatus
ninenines cowlib 2.9.0< * affected
f017f8a0ecbffd5033d9ab49bf180186f7a523a7< * affected
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I. Basic Information for CVE-2026-43969

Vulnerability Information
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Vulnerability Title
Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1
Source: CVE Program / CVE List V5
Vulnerability Description
Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields. cow_cookie:cookie/1 in cowlib builds a client-side Cookie: request header from a list of name-value pairs without validating either field. An attacker who controls the cookie names or values passed to this function can inject ;, ,, CR, LF, or TAB characters into the serialized header. This enables two classes of attack: cookie smuggling within a single header (e.g. injecting ; admin=1 to introduce a phantom cookie that the receiving server treats as authentic) and HTTP request header splitting (injecting CRLF to append arbitrary headers or smuggle a complete second request against a shared upstream proxy). The decoder side (parse_cookie_name/1, parse_cookie_value/1) and setcookie/3 already validate and reject these characters; the encoder alone is missing the check. This issue affects cowlib: from 2.9.0 onward.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/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 2.9.0版本存在注入漏洞，该漏洞源于cow_cookie:cookie/1在cowlib中从名称值对列表构建客户端Cookie请求标头而未验证任一字段，控制cookie名称或值的攻击者可向序列化标头注入;、、、CR、LF或TAB字符，实现cookie走私和HTTP请求标头分割攻击。
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 2.9.0 ~ * cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*
ninenines cowlib f017f8a0ecbffd5033d9ab49bf180186f7a523a7 ~ * cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-43969

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III. Intelligence Information for CVE-2026-43969

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Patches & Fixes for CVE-2026-43969 (1)

Vendor Advisories for CVE-2026-43969 (2)

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

CVE-2026-7790 Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS
CVE-2026-43968 CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-43969

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