OpenSSL 1

tenable:122504 maps to CVE-2019-1559, OpenSSL’s 0-byte record padding oracle fixed in OpenSSL 1.0.2r. Upstream affected versions are 1.0.2 through 1.0.2q; OpenSSL 1.1.0 and 1.1.1 are not affected. The bug only becomes useful when a TLS endpoint using legacy TLS 1.2 CBC cipher suites hits a fatal protocol error, the application then calls SSL_shutdown() twice, and the platform ends up using a non-stitched CBC implementation.

The vendor MEDIUM label is technically defensible, but operationally it is too hot for most enterprise patch queues. This is not a one-packet internet RCE; it is a confidentiality bug that usually needs an active man-in-the-middle position, legacy cipher negotiation, and a very specific application misuse pattern. That stack of prerequisites sharply narrows the reachable population, so for most 10,000-host environments this belongs in backlog hygiene / crypto-hardening, not emergency response.

Why this verdict

• Downgrade for attacker position: a practical exploit normally assumes the attacker is already on path to the victim's TLS session, which is a major real-world gate.
• Downgrade for implementation friction: exploitability needs legacy TLS 1.2 CBC plus a non-stitched ciphersuite path plus an application that calls SSL_shutdown() twice after a fatal error.
• Downgrade for blast radius: successful exploitation decrypts or hijacks observed sessions; it does not hand you unauthenticated server-side code execution across the fleet.

Why not higher?

This is not an unauthenticated edge takeover, and it is not a low-complexity internet spray target. Even where OpenSSL 1.0.2 is present, many deployments negotiate AEAD suites first, use stitched CBC implementations, or never hit the vulnerable application behavior.

Why not lower?

It is still a real confidentiality flaw in a foundational crypto library, public research and scanner tooling exist, and some legacy internet-facing estates still enable CBC. If you run exposed 1.0.2-era TLS endpoints for browsers or APIs, you should not ignore it completely.

1. Disable CBC cipher suites where business-safe — Remove legacy TLS 1.2 CBC suites from internet-facing listeners and load balancers first; that cuts off the vulnerable exploit path even before you touch packages. For a LOW verdict there is no formal SLA, so do this during normal crypto-hardening/backlog work rather than as an emergency outage.
2. Prefer AEAD-only TLS policies — Force modern suites such as AES-GCM or ChaCha20-Poly1305 so vulnerable CBC handling never gets negotiated. Fold this into your standard TLS baseline refresh; again, LOW means backlog hygiene, not a war room.
3. Verify distro backports before declaring exposure — A lot of hosts still show 1.0.2* in package names even when the fix is backported by the distro. Validate package release numbers against vendor advisories before burning patch capacity on false positives.
4. Retire OpenSSL 1.0.2 estates — The bigger risk story is that 1.0.2 reached end of support on 2019-12-31. Use this finding as fuel to remove legacy TLS stacks during your platform refresh cycle, because future crypto issues will keep landing on the same old estate.

Run this on the target Linux host that actually provides or links against OpenSSL, not from your scanner node. Invoke it as bash check-cve-2019-1559.sh or sudo bash check-cve-2019-1559.sh; root is helpful for package queries but usually not required. The script checks common distro backports first, then falls back to upstream version logic and prints VULNERABLE, PATCHED, or UNKNOWN.

#!/usr/bin/env bash
# check-cve-2019-1559.sh
# Purpose: Assess likely exposure to CVE-2019-1559 (OpenSSL 0-byte record padding oracle)
# Output: VULNERABLE / PATCHED / UNKNOWN
# Exit codes: 0=PATCHED, 1=VULNERABLE, 2=UNKNOWN

set -u

say() { echo "$1"; }
ver_ge() {
  # crude but workable lexicographic version compare for these package/version families
  # returns 0 if $1 >= $2
  [ "$(printf '%s\n%s\n' "$1" "$2" | sort -V | tail -n1)" = "$1" ]
}

OS_ID=""
OS_VER=""
if [ -r /etc/os-release ]; then
  . /etc/os-release
  OS_ID="${ID:-}"
  OS_VER="${VERSION_ID:-}"
fi

OPENSSL_BIN_VER=""
if command -v openssl >/dev/null 2>&1; then
  OPENSSL_BIN_VER="$(openssl version 2>/dev/null | awk '{print $2}')"
fi

# 1) Debian/Ubuntu package checks with known fixed backports
if command -v dpkg-query >/dev/null 2>&1; then
  PKG=""
  PKGVER=""

  for p in libssl1.0.0 openssl1.0 openssl; do
    if dpkg-query -W -f='${Status} ${Version}\n' "$p" 2>/dev/null | grep -q 'install ok installed'; then
      PKG="$p"
      PKGVER="$(dpkg-query -W -f='${Version}' "$p" 2>/dev/null)"
      break
    fi
  done

  if [ -n "$PKG" ] && [ -n "$PKGVER" ]; then
    case "$OS_ID:$OS_VER" in
      ubuntu:16.04)
        if ver_ge "$PKGVER" "1.0.2g-1ubuntu4.15"; then say "PATCHED"; exit 0; else say "VULNERABLE"; exit 1; fi ;;
      ubuntu:18.04)
        if ver_ge "$PKGVER" "1.0.2n-1ubuntu5.3"; then say "PATCHED"; exit 0; else say "VULNERABLE"; exit 1; fi ;;
      ubuntu:18.10)
        if ver_ge "$PKGVER" "1.0.2n-1ubuntu6.2"; then say "PATCHED"; exit 0; else say "VULNERABLE"; exit 1; fi ;;
      debian:9)
        if ver_ge "$PKGVER" "1.0.2r-1~deb9u1"; then say "PATCHED"; exit 0; else say "VULNERABLE"; exit 1; fi ;;
    esac

    # Unknown Debian-family release with a 1.0.2 package: avoid lying about backports
    if echo "$PKGVER" | grep -q '1\.0\.2'; then
      say "UNKNOWN"
      exit 2
    fi
  fi
fi

# 2) RPM family check for RHEL/CentOS/Oracle Linux 7 backport
if command -v rpm >/dev/null 2>&1; then
  if rpm -q openssl >/dev/null 2>&1; then
    RPMVER="$(rpm -q --qf '%{VERSION}-%{RELEASE}\n' openssl 2>/dev/null)"
    case "$OS_ID:$OS_VER" in
      rhel:7*|centos:7*|ol:7*|rocky:7*|almalinux:7*)
        if ver_ge "$RPMVER" "1.0.2k-19.el7"; then say "PATCHED"; exit 0; else say "VULNERABLE"; exit 1; fi ;;
    esac

    # If changelog explicitly mentions the CVE, trust the vendor backport.
    if rpm -q --changelog openssl 2>/dev/null | grep -q 'CVE-2019-1559'; then
      say "PATCHED"
      exit 0
    fi

    if echo "$RPMVER" | grep -q '^1\.0\.2'; then
      say "UNKNOWN"
      exit 2
    fi
  fi
fi

# 3) Upstream/OpenSSL binary fallback
if [ -n "$OPENSSL_BIN_VER" ]; then
  case "$OPENSSL_BIN_VER" in
    1.0.2|1.0.2[a-q])
      say "VULNERABLE"
      exit 1
      ;;
    1.0.2r|1.0.2s|1.0.2t|1.0.2u)
      say "PATCHED"
      exit 0
      ;;
    1.1.0*|1.1.1*|3.*)
      say "PATCHED"
      exit 0
      ;;
  esac
fi

say "UNKNOWN"
exit 2

Sources

1. Tenable Nessus Plugin 122504
2. OpenSSL Security Advisory 2019-02-26
3. NVD CVE-2019-1559
4. Ubuntu USN-3899-1
5. Debian DSA-4400-1 via OSV
6. Red Hat RHSA-2019:2304
7. TLS Padding Oracles research repo
8. USENIX paper: Scalable Scanning and Automatic Classification of TLS Padding Oracle Vulnerabilities