CVE-2026-43972: Gun Gun_http2 Has An Origin Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-36w4-95hv-5vwg
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CWE-346
Published
Advisory Summary

CVE-2026-43972 is a MODERATE gun_http2 has an origin validation vulnerability (CWE-346: Origin Validation Error) affecting Gun libraries in the Hex ecosystem. The issue involves gun_http2 has an origin validation error vulnerability. Remediation is available by upgrading affected packages to version 2.4.0.

CVE-2026-43972 at a Glance

CVE Identifier CVE-2026-43972
GHSA Identifier GHSA-36w4-95hv-5vwg
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-346: Origin Validation Error
Affected Product Gun
Package Ecosystem Hex
Published Date
Last Updated

How to Fix CVE-2026-43972

To remediate this vulnerability, upgrade all affected Gun dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

gun fixed: 2.4.0 
Upgrade gun to 2.4.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for gun

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-43972, inspect your project dependencies for Gun:

inspect dependencies for gun

Analyze the terminal output to locate any version of Gun in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.4.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-346: Origin Validation Error, where the product does not properly verify that the source of data or communication is valid. In Gun, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority. In gun_http2:push_promise_frame/7, the :authority pseudo-header from an incoming PUSH_PROMISE frame is stored verbatim into the promised stream record without checking that it matches the connection's origin. When gun_http2:headers_frame/9 later processes the response headers for the promised stream, it calls gun_cookies:set_cookie_header/7 with the unvalidated server-supplied authority before any status branching and before user code can act. This violates RFC 7540 §10.6 / RFC 9113 §8.4, which require receivers to treat as a protocol error any push for a resource the server is not authoritative for. A malicious or compromised HTTP/2 server can plant cookies scoped to arbitrary third-party domains into the client's shared cookie store. This enables session fixation attacks against those domains and, if the planted cookie overrides a legitimate session token, may result in account takeover. No user interaction beyond making a normal HTTP/2 request to the attacker-controlled server is required. This issue affects gun: from 2.0.0 before 2.4.0.

CVE-2026-43972 Affected Gun Versions

1 component(s)
Fixed Versions:
2.4.0
Product / Package Ecosystem Affected Versions Fixed Version
gun
 Hex
≥ 2.0.0
< 2.4.0
2.4.0

References

NVD — CVE-2026-43972 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-43972
Security Fix Commit FIX COMMIT
https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676
cna.erlef.org/cves/cve-2026-43972... WEB
https://cna.erlef.org/cves/CVE-2026-43972.html
Gun Source Repository REPOSITORY
https://github.com/ninenines/gun
osv.dev/vulnerability/eef-c... WEB
https://osv.dev/vulnerability/EEF-CVE-2026-43972

Frequently Asked Questions

What is CVE-2026-43972?
CVE-2026-43972 is a security vulnerability in Gun involving gun_http2 has an Origin Validation Error vulnerability under CWE-346: Origin Validation Error.
Which Gun versions are affected?
Affected versions include releases prior to 2.4.0 across affected packages: gun.
What version fixes CVE-2026-43972?
Upgrading to 2.4.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is gun affected?
Yes, gun is affected in releases prior to 2.4.0. Upgrade your dependency to 2.4.0 or later.
What CWE is associated with CVE-2026-43972?
CVE-2026-43972 is classified under CWE-346: Origin Validation Error (The product does not properly verify that the source of data or communication is valid.).
How can I check Hex dependencies for CVE-2026-43972?
Run the dependency tree command: 'inspect dependencies for gun'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-36w4-95hv-5vwg",
  "modified" : "2026-07-29T15:44:30Z",
  "published" : "2026-06-08T15:32:59Z",
  "aliases" : [ "CVE-2026-43972" ],
  "summary" : "gun_http2 has an Origin Validation Error vulnerability",
  "details" : "Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority.\n\nIn gun_http2:push_promise_frame/7, the :authority pseudo-header from an incoming PUSH_PROMISE frame is stored verbatim into the promised stream record without checking that it matches the connection's origin. When gun_http2:headers_frame/9 later processes the response headers for the promised stream, it calls gun_cookies:set_cookie_header/7 with the unvalidated server-supplied authority before any status branching and before user code can act. This violates RFC 7540 §10.6 / RFC 9113 §8.4, which require receivers to treat as a protocol error any push for a resource the server is not authoritative for.\n\nA malicious or compromised HTTP/2 server can plant cookies scoped to arbitrary third-party domains into the client's shared cookie store. This enables session fixation attacks against those domains and, if the planted cookie overrides a legitimate session token, may result in account takeover. No user interaction beyond making a normal HTTP/2 request to the attacker-controlled server is required.\n\nThis issue affects gun: from 2.0.0 before 2.4.0.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "gun"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-43972"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-43972.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ninenines/gun"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-43972"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-346" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-29T15:44:30Z",
    "nvd_published_at" : "2026-06-08T15:16:46Z"
  }
}