OpenSSL 1

Tenable plugin 112119 bundles two OpenSSL issues fixed in 1.0.2p on 2018-08-14. CVE-2018-0732 affects 1.0.2 through 1.0.2o and lets a malicious TLS server send an oversized DH parameter so the client burns CPU and appears hung during the handshake. CVE-2018-0737 affects 1.0.2b through 1.0.2o and is a cache-timing side channel during RSA key generation; the attacker needs sufficient local/co-resident access while the victim is generating a key.

Tenable's MEDIUM label is generous for enterprise prioritization. In the real world this is not an internet-scale server compromise: one path is availability-only and client-side, the other is local side-channel access during a relatively infrequent operation. If you still run OpenSSL 1.0.2, the bigger problem is that the branch has been out of public support since 2020-01-01; that lifecycle debt matters more than these two specific bugs.

Why this verdict

• Requires the wrong side of the connection: CVE-2018-0732 is fundamentally a client-side handshake DoS, so it misses the large population of inbound-only TLS servers that defenders instinctively worry about.
• Local/co-resident prerequisite crushes scale: CVE-2018-0737 assumes a prior foothold or shared-host visibility during RSA key generation, which is already post-initial-access and operationally narrow.
• Blast radius is small even when triggered: the DoS path usually hangs a process or session, and the keygen path targets a specific key creation event rather than enabling durable remote code execution.

Why not higher?

This is not a pre-auth remote server compromise, not wormable, and not tied to strong public evidence of active exploitation. The strongest-looking score in the ecosystem comes from abstract CVSS modeling, but the real exploit chains are hemmed in by client role, local access, and timing requirements.

Why not lower?

It is still a real bug set in a foundational crypto library, and vulnerable 1.0.2 estates usually signal broader hygiene problems. If a host regularly makes outbound TLS connections to untrusted destinations, or if shared infrastructure generates sensitive RSA keys, the finding is not ignorable.

1. Prefer package-vendor fixes over raw upstream version checks — Validate whether your distro already backported the fixes before you launch a noisy patch campaign. For a LOW finding there is no SLA; do this during normal triage and close false positives quickly so your team does not waste backlog capacity.
2. Reduce or disable legacy DHE where feasible — For the client-side DoS path, shrinking DH(E) negotiation opportunities lowers exposure. Fold cipher-suite hardening into your next normal maintenance cycle; there is no emergency deadline here unless the application is a high-risk outbound client to untrusted servers.
3. Constrain local multi-tenant execution — The RSA keygen side-channel matters far less on well-isolated hosts. Keep strong tenant isolation, limit shell access, and avoid generating long-lived keys on shared or weakly isolated systems as standard platform hygiene.
4. Retire OpenSSL 1.0.2 strategically — Even though this plugin is LOW, the branch itself is EOL. Use your routine remediation program to migrate off 1.0.2; that platform-lifecycle work is more valuable than treating this plugin as a fire drill.

Run this on the target Linux/macOS host that Tenable flagged, not from your scanner. Invoke it as bash verify_openssl_102p.sh; root is not required, but package-manager access helps it distinguish vulnerable upstream 1.0.2x builds from patched distro backports. The script exits 0 for PATCHED, 1 for VULNERABLE, and 2 for UNKNOWN.

#!/usr/bin/env bash
# verify_openssl_102p.sh
# Checks whether the local host appears vulnerable to the OpenSSL 1.0.2 < 1.0.2p bundle
# (Tenable plugin 112119 / CVE-2018-0732 + CVE-2018-0737).
# Exit codes: 0=PATCHED, 1=VULNERABLE, 2=UNKNOWN

set -u
PATH=/usr/sbin:/usr/bin:/sbin:/bin

say() { printf '%s\n' "$*"; }
patched() { say "PATCHED - $*"; exit 0; }
vuln() { say "VULNERABLE - $*"; exit 1; }
unknown() { say "UNKNOWN - $*"; exit 2; }

if ! command -v openssl >/dev/null 2>&1; then
  unknown "openssl binary not found in PATH"
fi

ver_line="$(openssl version 2>/dev/null || true)"
if [[ -z "$ver_line" ]]; then
  unknown "could not execute 'openssl version'"
fi

# Extract upstream-looking OpenSSL version token.
if [[ "$ver_line" =~ OpenSSL[[:space:]]([0-9]+\.[0-9]+\.[0-9]+[a-z]?) ]]; then
  upstream_ver="${BASH_REMATCH[1]}"
else
  unknown "could not parse OpenSSL version from: $ver_line"
fi

# Distro-backport checks first, because package versions may be fixed while reporting 1.0.2n/g/f etc.
if command -v dpkg-query >/dev/null 2>&1; then
  . /etc/os-release 2>/dev/null || true

  get_pkg_ver() {
    local p="$1"
    dpkg-query -W -f='${Version}' "$p" 2>/dev/null || true
  }

  # Ubuntu fixed versions from USN-3692-1 for this advisory set.
  if [[ "${ID:-}" == "ubuntu" ]]; then
    pkg_ver="$(get_pkg_ver libssl1.0.0)"
    if [[ -n "$pkg_ver" ]]; then
      case "${VERSION_ID:-}" in
        18.04)
          dpkg --compare-versions "$pkg_ver" ge 1.0.2n-1ubuntu5.1 && patched "Ubuntu 18.04 backport detected: libssl1.0.0 $pkg_ver"
          ;;
        17.10)
          dpkg --compare-versions "$pkg_ver" ge 1.0.2g-1ubuntu13.6 && patched "Ubuntu 17.10 backport detected: libssl1.0.0 $pkg_ver"
          ;;
        16.04)
          dpkg --compare-versions "$pkg_ver" ge 1.0.2g-1ubuntu4.13 && patched "Ubuntu 16.04 backport detected: libssl1.0.0 $pkg_ver"
          ;;
        14.04)
          dpkg --compare-versions "$pkg_ver" ge 1.0.1f-1ubuntu2.26 && patched "Ubuntu 14.04 backport detected: libssl1.0.0 $pkg_ver"
          ;;
      esac
    fi
  fi

  # Debian stretch openssl1.0 backport noted in Debian tracker.
  if [[ "${ID:-}" == "debian" || "${ID_LIKE:-}" == *debian* ]]; then
    pkg_ver="$(get_pkg_ver openssl1.0)"
    if [[ -n "$pkg_ver" ]]; then
      dpkg --compare-versions "$pkg_ver" ge 1.0.2q-1~deb9u1 && patched "Debian openssl1.0 backport detected: $pkg_ver"
    fi
  fi
fi

# Upstream-style version logic.
# Vulnerable ranges:
# - CVE-2018-0732: 1.0.2 .. 1.0.2o
# - CVE-2018-0737: 1.0.2b .. 1.0.2o
# Plugin logic: any OpenSSL prior to 1.0.2p.
case "$upstream_ver" in
  1.0.2|1.0.2[a-o])
    vuln "upstream OpenSSL version appears older than 1.0.2p ($upstream_ver)"
    ;;
  1.0.2[p-z]|1.0.2za|1.0.2zb|1.0.2zc|1.0.2zd|1.0.2ze|1.0.2zf|1.0.2zg|1.0.2zh|1.0.2zi|1.0.2zj|1.0.2zk|1.0.2zl|1.0.2zm)
    patched "upstream OpenSSL version is 1.0.2p or later ($upstream_ver)"
    ;;
  0.*|1.1.*|3.*|2.*)
    patched "host is not on the affected upstream 1.0.2 < 1.0.2p branch ($upstream_ver)"
    ;;
  *)
    unknown "unable to safely classify version '$upstream_ver'; check vendor backports/changelog manually"
    ;;
esac

Sources

1. Tenable Nessus Plugin 112119
2. OpenSSL Security Advisory 2018-06-12 (CVE-2018-0732)
3. OpenSSL Security Advisory 2018-04-16 (CVE-2018-0737)
4. NVD CVE-2018-0732
5. NVD CVE-2018-0737
6. Ubuntu USN-3692-1 OpenSSL vulnerabilities
7. Debian tracker CVE-2018-0732
8. IACR ePrint: Cache-Timing Attacks on RSA Key Generation