PT-2026-47299 · Ninenines · Gun

Loïc Hoguin

+1

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Published

2026-06-08

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Updated

2026-06-08

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CVE-2026-43973

CVSS v4.0

8.7

High

VectorAV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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 r 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 r 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 OKr X-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.

Fix

Allocation of Resources Without Limits

Weakness Enumeration

CWE-770

Related Identifiers

CVE-2026-43973

Affected Products

Gun