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CVE-2026-43973— gun HTTP/1.1 response buffer has no size limit allowing server-controlled memory exhaustion

Quick assessment

Affected
ninenines gun
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.

Gun是Nine Nines开源的一款支持HTTP/1.1、HTTP/2和WebSocket的Erlang HTTP客户端。 gun 1.0.0版本至2.4.0之前版本存在安全漏洞，该漏洞源于gun_http模块存在不受控制的资源消耗，可能导致恶意服务器通过无限制的HTTP/1.1响应缓冲耗尽客户端内存。

AI Predicted 7.5 Difficulty: Easy EPSS 0.64% · P50

Affected Version Matrix 2

VendorProduct Version RangeStatus
ninenines gun 1.0.0< 2.4.0 affected
11dfe71f4b9aedaaedea2ad3b2f32fd006a8480f< f3e7e0568b3c4cf9fa4bea79d5116e67ce76ad25 affected
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I. Basic Information for CVE-2026-43973

Vulnerability Information
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Vulnerability Title
gun HTTP/1.1 response buffer has no size limit allowing server-controlled memory exhaustion
Source: CVE Program / CVE List V5
Vulnerability Description
Uncontrolled Resource Consumption vulnerability in ninenines gun (gun_http module) allows a malicious server to exhaust client memory via unbounded HTTP/1.1 response buffering. In gun_http:handle/5, three clauses accumulate incoming TCP data into the connection's buffer field using binary concatenation with no upper-bound check: the head clause appends data until the \r\n\r\n header terminator is found; the body_chunked clause appends data whenever cow_http_te:stream_chunked/2 returns a more result indicating an incomplete chunk boundary; and the body_trailer clause appends data until the trailing \r\n\r\n is found. In each case, when the expected terminator never arrives, the enlarged binary is stored back into state and the process waits for more data, with no configurable or hard-coded ceiling on buffer size. A malicious or compromised server can exploit this by sending a partial response that never completes. For example, a response may begin with HTTP/1.1 200 OK\r\nX-Pad: followed by an unbounded stream of arbitrary bytes, never sending the header terminator. The gun connection process will continuously append the incoming data to its buffer, causing unbounded heap growth. Because BEAM imposes no per-process heap limit by default, a single malicious connection can exhaust all available memory on the node, causing a node-wide out-of-memory crash. This issue affects gun: from 1.0.0 before 2.4.0.
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
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Gun 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Gun是Nine Nines开源的一款支持HTTP/1.1、HTTP/2和WebSocket的Erlang HTTP客户端。 gun 1.0.0版本至2.4.0之前版本存在安全漏洞，该漏洞源于gun_http模块存在不受控制的资源消耗，可能导致恶意服务器通过无限制的HTTP/1.1响应缓冲耗尽客户端内存。
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 gun 1.0.0 ~ 2.4.0 cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*
ninenines gun 11dfe71f4b9aedaaedea2ad3b2f32fd006a8480f ~ f3e7e0568b3c4cf9fa4bea79d5116e67ce76ad25 cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-43973

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III. Intelligence Information for CVE-2026-43973

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Patches & Fixes for CVE-2026-43973 (1)

Vendor Advisories for CVE-2026-43973 (2)

Same Patch Batch · ninenines · 2026-06-08 · 4 CVEs total

CVE-2026-43966 6.3 MEDIUM HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2
CVE-2026-43972 gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-ori
CVE-2026-43974 gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-d

IV. Related Vulnerabilities

Same product: gun
Same vendor: ninenines
Same weakness: CWE-770

V. Comments for CVE-2026-43973

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