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VulnerabilityPublished

CVE-2026-43974: ninenines gun · Improper Enforcement of Behavioral Workflow

Affects ninenines gunSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 2.4.0 soon.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.4.0, 5b48068c29ce5e112cb149b5857c7d4dc319a81b
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade gun and ninenines/gun to 2.4.0; gun to 5b48068c29ce5e112cb149b5857c7d4dc319a81b.

Affected software

ProductAffectedFixed in
nineninesgunAffected
  • >=2.0.0 <2.4.0
Fixed in
  • 2.4.0
nineninesgunAffected
  • ≥ a3c2edbb8c807717e2f10520c6cf1e77a62eab2e, < 5b48068c29ce5e112cb149b5857c7d4dc319a81b
Fixed in
  • 5b48068c29ce5e112cb149b5857c7d4dc319a81b
Hexninenines/gunpkg:hex/ninenines/gunOther threatsAffected
  • >=2.0.0 <2.4.0
  • =2.0.0
Fixed in
  • 2.4.0
GitHubgunpkg:github/gunOther threatsAffected
  • >=2.0.0 <2.4.0
Fixed in
  • 2.4.0

CPE configurations (1)

  • cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users should avoid using vulnerable versions or mitigate exposure to untrusted HTTP servers.

Description

CVE-2026-43974 is a high-severity vulnerability in the ninenines gun HTTP client (gun_http module) that allows a malicious HTTP server to force the client into raw protocol mode by sending an unsolicited 101 Switching Protocols response. This causes the client to abandon HTTP framing and accept unbounded data, potentially exhausting memory and crashing the Erlang VM. The issue affects gun versions from 2.0.0 up to but not including 2.4.0.

References

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