{
  "cveId": "CVE-2026-43971",
  "url": "https://patchblox.com/security/cve/CVE-2026-43971",
  "summary": "CVE-2026-43971 is fixed in erlang-cowlib on 1 platform by DEBIAN-CVE-2026-43971 (version 2.20.0-1), released August 18, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "Link Header Directive Smuggling via Unescaped target/rel/Attribute Keys in cow_link:link/1",
  "description": "Improper Encoding or Escaping of Output vulnerability in ninenines cowlib allows Link header directive smuggling via unescaped special characters in cow_link:link/1.  cow_link:do_link/1 in cowlib interpolates the target URI, rel value, and attribute keys directly into the serialized Link: header value without escaping or token-grammar validation. A \u003E byte in target prematurely closes the URI slot, allowing an attacker to append additional link entries with attacker-chosen rel directives. A \u0022 or \\ in rel escapes the quoted string and opens new parameters. Any byte \u2014 including whitespace, =, and \u0022 \u2014 in an attribute key is emitted verbatim. Because browsers act on Link: directives such as rel=\u0022preconnect\u0022, rel=\u0022preload\u0022, and rel=\u0022prerender\u0022, an attacker who can influence these fields in an application that round-trips parsed Link headers through cow_link:link/1 can force victim browsers to make out-of-band connections to attacker-controlled origins.  This issue affects cowlib: from 2.9.0 before 2.20.0.",
  "published": "2026-08-18T09:17:14Z",
  "severity": "Moderate",
  "cwe": "Improper Encoding or Escaping of Output",
  "epss": 0.00524,
  "epssPercentile": 0.44661,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43971",
  "fixes": [
    {
      "platform": "linux",
      "product": "erlang-cowlib",
      "release": "Debian 14",
      "fixedVersion": "2.20.0-1",
      "fix": "DEBIAN-CVE-2026-43971",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-43971",
      "released": "2026-08-18T09:17:14Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T00:53:09Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}