{
  "cveId": "CVE-2026-66035",
  "url": "https://patchblox.com/security/cve/CVE-2026-66035",
  "summary": "CVE-2026-66035 is fixed in 6 products on 1 platform, first by libssh2-1t64 1.11.0-4.1ubuntu0.24.04.4, released July 24, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "libssh2 Heap Buffer Overflow via ETM Cipher Negotiation",
  "description": "libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length smaller than the cipher\u0027s block size during Encrypt-then-MAC cipher negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit glibc writes attacker-controlled bytes into an adjacent chunk\u0027s SIZE field, enabling tcache bin confusion, overlapping live objects, and function pointer overwrite during the session handshake before authentication.",
  "published": "2026-07-24T10:17:00Z",
  "severity": "Important",
  "cvss": 7.5,
  "cwe": "Heap-based Buffer Overflow",
  "epss": 0.00472,
  "epssPercentile": 0.41041,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66035",
  "fixes": [
    {
      "platform": "linux",
      "product": "cargo-c",
      "release": "amzn 2023",
      "fixedVersion": "0.10.21-1.amzn2023.0.1",
      "fix": "ALAS2023-2026-2064",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2064",
      "released": "2026-08-17T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "cargo-c-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "0.10.21-1.amzn2023.0.1",
      "fix": "ALAS2023-2026-2064",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2064",
      "released": "2026-08-17T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "libssh2",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "1.11.1-1\u002Bdeb13u2",
      "fix": "DEBIAN-CVE-2026-66035",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-66035",
      "released": "2026-08-01T14:28:19Z"
    },
    {
      "platform": "linux",
      "product": "libssh2",
      "release": "Debian 14",
      "fixedVersion": "1.11.1-5",
      "fix": "DEBIAN-CVE-2026-66035",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-66035",
      "released": "2026-08-01T14:28:19Z"
    },
    {
      "platform": "linux",
      "product": "libssh2-1t64",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.11.0-4.1ubuntu0.24.04.4",
      "fix": "libssh2-1t64 1.11.0-4.1ubuntu0.24.04.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-libssh2-1t64-1.11.0-4.1ubuntu0.24.04.4",
      "released": "2026-07-24T10:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libssh2-1t64",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.11.1-1ubuntu0.26.04.4",
      "fix": "libssh2-1t64 1.11.1-1ubuntu0.26.04.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-libssh2-1t64-1.11.1-1ubuntu0.26.04.4",
      "released": "2026-07-24T10:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libssh2_org",
      "release": "opensuse-leap 16.0",
      "fixedVersion": "1.11.1-160000.5.1",
      "fix": "OPENSUSE-SU-2026:21549-1",
      "url": "https://patchblox.com/security/fix/linux/opensuse-su-2026-21549-1",
      "released": "2026-08-10T15:24:32Z"
    },
    {
      "platform": "linux",
      "product": "libssh2_org",
      "release": "sles 15.6",
      "fixedVersion": "1.11.0-150600.20.6.1",
      "fix": "SUSE-SU-2026:3541-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-3541-1",
      "released": "2026-08-10T12:50:14Z"
    },
    {
      "platform": "linux",
      "product": "libssh2_org",
      "release": "sles 15.7",
      "fixedVersion": "1.11.0-150600.20.6.1",
      "fix": "SUSE-SU-2026:3541-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-3541-1",
      "released": "2026-08-10T12:50:14Z"
    },
    {
      "platform": "linux",
      "product": "libssh2_org",
      "release": "sles 16.0",
      "fixedVersion": "1.11.1-160000.5.1",
      "fix": "SUSE-SU-2026:23225-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-23225-1",
      "released": "2026-08-10T15:24:14Z"
    },
    {
      "platform": "linux",
      "product": "rust-cargo-c-debugsource",
      "release": "amzn 2023",
      "fixedVersion": "0.10.21-1.amzn2023.0.1",
      "fix": "ALAS2023-2026-2064",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2064",
      "released": "2026-08-17T09:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-07T18:46:35Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}