{
  "cveId": "CVE-2026-43966",
  "url": "https://patchblox.com/security/cve/CVE-2026-43966",
  "summary": "CVE-2026-43966 is fixed in erlang-cowboy on 1 platform by DEBIAN-CVE-2026-43966 (version 2.16.1\u002Bdfsg-1), released June 8, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2",
  "description": "Improper Neutralization of CRLF Sequences in HTTP Headers (\u0027HTTP Request/Response Splitting\u0027) vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.  cow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \u0022, passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding \u0022 and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.  This issue affects cowlib: from 2.9.0 onward.",
  "published": "2026-06-08T17:16:43Z",
  "severity": "Low",
  "cvss": 5.3,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
  "cwe": "Improper Neutralization of CRLF Sequences in HTTP Headers (\u0027HTTP Request/Response Splitting\u0027)",
  "epss": 0.00259,
  "epssPercentile": 0.17644,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43966",
  "fixes": [
    {
      "platform": "linux",
      "product": "erlang-cowboy",
      "release": "Debian 14",
      "fixedVersion": "2.16.1\u002Bdfsg-1",
      "fix": "DEBIAN-CVE-2026-43966",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-43966",
      "released": "2026-06-08T17:16:43Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}