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🛡️ CVE-2026-43973 — gun

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-770 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

Summary

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: 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

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-43973 is classified as CWE-770: Allocation of Resources Without Limits. Resources are allocated on request with no cap, so a client can exhaust them.

Affected software

CVE-2026-43973 is recorded against 1 package.

  • gun

Timeline and source

Published on 8 June 2026 and last revised on 18 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from OSV.

References

nvd.nist.gov (Advisory)
github.com (Web)
cna.erlef.org (Web)
github.com (Package)
osv.dev (Web)

Other advisories for this package

gun has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-770: Allocation of Resources Without Limits) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector 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
CWE CWE-770
Public Exploit ✅ No
Source OSV
Published 2026-06-08
Updated 2026-08-20
Modified 2026-08-18

Affected Packages

Software From version Fixed in
gun — —

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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