PHP 5

This issue maps to CVE-2018-14883 in PHP's EXIF handling. Upstream affected versions are PHP before 5.6.37, 7.0.x before 7.0.31, 7.1.x before 7.1.20, and 7.2.x before 7.2.8; your Tenable plugin is the 5.6.x < 5.6.37 slice. The bug is an integer overflow in exif_thumbnail_extract() that can lead to a heap-based out-of-bounds read when a PHP application parses attacker-controlled image metadata.

The vendor-style 7.5/High score overstates enterprise risk for patch prioritization. The decisive friction is that credible analysis from Red Hat says the overflow condition is 32-bit only, and the code path is reached only when the application actually invokes exif_thumbnail() or exif_read_data(..., ..., ..., true) on untrusted images; that is a much smaller population than 'every internet-facing PHP server.'

Why this verdict

• Downgrade: 32-bit runtime required. Red Hat explicitly notes the integer overflow condition only occurs on 32-bit builds, which is a major population cut.
• Downgrade: application reachability is narrow. The bug is only reached when the app calls exif_thumbnail() or exif_read_data() in the relevant mode on attacker-controlled content.
• Downgrade: impact is mostly DoS. The practical outcome is crash/instability or limited over-read, not straightforward remote code execution.

Why not higher?

I am not scoring this HIGH because the nominal network vector hides two compounding prerequisites: a 32-bit PHP runtime and a reachable EXIF parsing workflow on untrusted images. Those are exactly the kinds of real-world narrowing conditions that should drag a vulnerability down for fleet patch planning.

Why not lower?

I am not scoring this IGNORE because there is still a legitimate remote attack path in the subset of legacy environments that ingest user-supplied images and parse EXIF on 32-bit PHP. If you run old shared-hosting style stacks, embedded appliances, or odd legacy x86 builds, the bug is real enough to keep on the backlog.

1. Disable EXIF where unused — If the application does not need EXIF parsing, stop loading the EXIF extension or remove the package/module. For a LOW verdict there is no SLA; treat as backlog hygiene, but do it opportunistically during the next config maintenance window because it removes this path entirely.
2. Block EXIF functions in legacy apps — Use disable_functions = exif_read_data, exif_thumbnail, read_exif_data where compatibility allows. For this LOW item there is no SLA; treat as backlog hygiene, but it is a cheap guardrail on especially old shared PHP estates.
3. Strip metadata on upload — Normalize or re-encode inbound images so attacker-controlled EXIF metadata never reaches PHP's EXIF parser. Again, no SLA for LOW, but this is the right engineering fix for image-processing workflows that cannot yet leave old PHP behind.
4. Hunt 32-bit PHP first — Prioritize inventory for hosts where PHP is both 32-bit and EXIF-enabled; those are the only systems that materially matter for this CVE. For LOW, there is no SLA; treat as backlog hygiene, but this triage step prevents wasting cycles on the 64-bit majority.

Run this on the target host, not from an auditor workstation. Invoke it as bash check-cve-2018-14883.sh /usr/bin/php (or omit the path to use php from $PATH); no root is required, but you need access to the same PHP binary/config used by the application stack.

#!/usr/bin/env bash
# check-cve-2018-14883.sh
# Detects likely exposure to CVE-2018-14883 on a local PHP runtime.
# Outputs one of: VULNERABLE / PATCHED / UNKNOWN
# Exit codes: 0=PATCHED, 1=VULNERABLE, 2=UNKNOWN

set -u

PHP_BIN="${1:-php}"

if ! command -v "$PHP_BIN" >/dev/null 2>&1; then
  echo "UNKNOWN - PHP binary not found: $PHP_BIN"
  exit 2
fi

INFO="$($PHP_BIN -d display_errors=0 -r '
$ver = PHP_VERSION;
$intsize = PHP_INT_SIZE;
$arch = php_uname("m");
$loaded = extension_loaded("exif") ? "yes" : "no";
$f1 = function_exists("exif_read_data") ? "yes" : "no";
$f2 = function_exists("exif_thumbnail") ? "yes" : "no";
echo "version=$ver\n";
echo "int_size=$intsize\n";
echo "arch=$arch\n";
echo "exif_loaded=$loaded\n";
echo "exif_read_data=$f1\n";
echo "exif_thumbnail=$f2\n";
' 2>/dev/null)"

if [ -z "$INFO" ]; then
  echo "UNKNOWN - unable to query PHP runtime"
  exit 2
fi

VERSION="$(printf '%s
' "$INFO" | awk -F= '/^version=/{print $2}')"
INT_SIZE="$(printf '%s
' "$INFO" | awk -F= '/^int_size=/{print $2}')"
ARCH="$(printf '%s
' "$INFO" | awk -F= '/^arch=/{print $2}')"
EXIF_LOADED="$(printf '%s
' "$INFO" | awk -F= '/^exif_loaded=/{print $2}')"
EXIF_READ="$(printf '%s
' "$INFO" | awk -F= '/^exif_read_data=/{print $2}')"
EXIF_THUMB="$(printf '%s
' "$INFO" | awk -F= '/^exif_thumbnail=/{print $2}')"

vp_lt() {
  # returns 0 if $1 < $2
  "$PHP_BIN" -r 'exit(version_compare($argv[1], $argv[2], "<") ? 0 : 1);' "$1" "$2"
}

is_affected_version=1
case "$VERSION" in
  5.6.*)
    if vp_lt "$VERSION" "5.6.37"; then is_affected_version=0; fi
    ;;
  7.0.*)
    if vp_lt "$VERSION" "7.0.31"; then is_affected_version=0; fi
    ;;
  7.1.*)
    if vp_lt "$VERSION" "7.1.20"; then is_affected_version=0; fi
    ;;
  7.2.*)
    if vp_lt "$VERSION" "7.2.8"; then is_affected_version=0; fi
    ;;
  *)
    is_affected_version=1
    ;;
esac

if [ "$is_affected_version" -ne 0 ]; then
  echo "PATCHED - PHP version $VERSION is outside the upstream affected ranges for CVE-2018-14883"
  exit 0
fi

if [ "$EXIF_LOADED" != "yes" ] || { [ "$EXIF_READ" != "yes" ] && [ "$EXIF_THUMB" != "yes" ]; }; then
  echo "UNKNOWN - version $VERSION is in an affected range, but EXIF does not appear reachable in this runtime"
  exit 2
fi

if [ "$INT_SIZE" = "4" ]; then
  echo "VULNERABLE - PHP $VERSION is in the affected range, EXIF is enabled, and runtime appears 32-bit ($ARCH)"
  exit 1
fi

if [ "$INT_SIZE" = "8" ]; then
  echo "UNKNOWN - PHP $VERSION is in the affected range, but runtime appears 64-bit ($ARCH); Red Hat analysis says the overflow condition is 32-bit only"
  exit 2
fi

echo "UNKNOWN - could not determine architecture/risk precisely for PHP $VERSION"
exit 2

Sources

1. Tenable Nessus Plugin 111230
2. NVD CVE-2018-14883
3. PHP security bug 76423
4. PHP 5 ChangeLog 5.6.37
5. Red Hat Bugzilla analysis
6. Ubuntu CVE page
7. Debian security tracker
8. BitSight observation footprint