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CVE-2026-7790— Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS

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 0.6.0版本至2.16.1之前版本存在资源管理错误漏洞，该漏洞源于cow_http_te模块中分块传输编码解析器接受无限制的十六进制数字，可能导致CPU耗尽和内存放大，导致拒绝服务。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.79% · P56

Affected Version Matrix 2

VendorProduct Version RangeStatus
ninenines cowlib 0.6.0< 2.16.1 affected
8c0e428b012c59f553a264f285ed89d36f791e3e< a4b8039ce8c93ab00867ef6b7e888822c09f4369 affected
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I. Basic Information for CVE-2026-7790

Vulnerability Information
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Vulnerability Title
Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS
Source: CVE Program / CVE List V5
Vulnerability Description
Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation. The chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on each partial read and restarts from zero on resumption, raising the cost to O(N³). An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request with Transfer-Encoding: chunked and a very long chunk-size hex string to cause denial of service through CPU exhaustion and memory amplification. This vulnerability is associated with program file src/cow_http_te.erl and program routines cow_http_te:stream_chunked/2, cow_http_te:chunked_len/4. This issue affects cowlib: from 0.6.0 before 2.16.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
Cowlib 资源管理错误漏洞
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 0.6.0版本至2.16.1之前版本存在资源管理错误漏洞，该漏洞源于cow_http_te模块中分块传输编码解析器接受无限制的十六进制数字，可能导致CPU耗尽和内存放大，导致拒绝服务。
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 0.6.0 ~ 2.16.1 cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*
ninenines cowlib 8c0e428b012c59f553a264f285ed89d36f791e3e ~ a4b8039ce8c93ab00867ef6b7e888822c09f4369 cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-7790

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III. Intelligence Information for CVE-2026-7790

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Patches & Fixes for CVE-2026-7790 (1)

Vendor Advisories for CVE-2026-7790 (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-2026-43968 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-400

V. Comments for CVE-2026-7790

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