How to Fix CVE-2026-5588: Use of a broken or risky in BC-JAVA

By Sai Kiran Pandrala. Last verified: 2026-05-25.

What is CVE-2026-5588?

Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules), Legion of the Bouncy Castle Inc. BCPKIX-FIPS bcpkix on All (pkix modules), Legion of the Bouncy Castle Inc. BCPIX-LTS bcpkix on All (pkix modules).

Am I affected?

Run the version check that matches your platform:

# Linux
dpkg -s default-jdk 2>/dev/null | grep -i version
rpm -q default-jdk 2>/dev/null
default-jdk --version 2>/dev/null

Compare what you see against the Affected row above (Legion of the Bouncy Castle Inc. BC-JAVA 1.67 to <1.80.2, 1.81 to <1.81.1, 1.82 to <1.84; Legion of the Bouncy Castle Inc. BCPKIX-FIPS 2.0.6 to <2.0.11, 2.1.7 to <2.1.11; Legion of the Bouncy Castle Inc. BCPIX-LTS 2.73.7 to <2.73.11). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-5588

The primary fix is to upgrade BC-JAVA to the patched build. Use the commands for your platform below; the patched versions listed in the vendor advisory are: BC-JAVA 1.80.2; BC-JAVA 1.81.1; BC-JAVA 1.84; BCPKIX-FIPS 2.0.11 (and 2 more SKUs — see vendor advisory).

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade default-jdk
default-jdk --version 2>/dev/null || dpkg -s default-jdk | grep -i version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --security default-jdk -y
rpm -q default-jdk

SUSE / openSUSE

sudo zypper patch --category security
rpm -q default-jdk

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-5588 affecting Java
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-5588-fix-$(Get-Date -Format yyyyMMdd-HHmmss).log"
New-Item -ItemType Directory -Force (Split-Path $LogPath) | Out-Null
Start-Transcript -Path $LogPath -Append

try {
    Write-Host "[1/4] Detecting installed version of Java"
    $pkg = winget list --id "Java" 2>$null
    Write-Host $pkg

    Write-Host "[2/4] Backing up configuration"
    $backup = "C:\Backup\Java-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\Java" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Applying upgrade to BC-JAVA 1.80.2; BC-JAVA 1.81.1; BC-JAVA 1.84; BCPKIX-FIPS 2.0.11 (and 2 more ..."
    winget upgrade --id "Java" --silent --accept-source-agreements --accept-package-agreements
    # Fallback: Windows Update for OS-level fixes
    if ($LASTEXITCODE -ne 0) {
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verifying patched build"
    winget list --id "Java"
    Write-Host "Fix applied. Reboot if prompted."
    exit 0
} catch {
    Write-Error "Patch failed: $_"
    exit 1
} finally {
    Stop-Transcript
}

Complete Bash remediation script (Linux)

#!/usr/bin/env bash
# Fix script for CVE-2026-5588 affecting Java
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-5588-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Detecting installed version"
if command -v dpkg >/dev/null; then
    dpkg -s default-jdk 2>/dev/null | grep -i version || echo "default-jdk not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q default-jdk || echo "default-jdk not installed via rpm"
fi

echo "[2/4] Backing up configuration"
BACKUP="/root/backup-cve-2026-5588-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/default-jdk /etc/default-jdk.d /etc/default-jdk.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Applying upgrade (target: BC-JAVA 1.80.2; BC-JAVA 1.81.1; BC-JAVA 1.84; BCPKIX-FIPS 2.0.11 (and 2 more ...)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y default-jdk
elif command -v dnf >/dev/null; then
    dnf upgrade --security -y default-jdk
elif command -v yum >/dev/null; then
    yum update -y default-jdk
elif command -v zypper >/dev/null; then
    zypper --non-interactive patch --category security
fi

echo "[4/4] Verifying patched build"
if command -v dpkg >/dev/null; then
    dpkg -s default-jdk 2>/dev/null | grep -i version
elif command -v rpm >/dev/null; then
    rpm -q default-jdk
fi
echo "Done. Restart any running daemons that loaded the old library."

If you can't patch immediately

If you cannot apply the patched version today, restrict exposure with one of the following runnable controls. None replace the patch.

Network restriction (Linux, nftables)

# Block inbound traffic to the affected service from untrusted networks
sudo nft add table inet filter
sudo nft 'add chain inet filter input { type filter hook input priority 0 ; }'
sudo nft 'add rule inet filter input tcp dport {443, 80} ip saddr != 10.0.0.0/8 drop'
sudo nft list ruleset

Service-level fallback

# If the affected feature is optional, stop the service until the patch is applied
sudo systemctl stop default-jdk
sudo systemctl disable default-jdk

How to verify the fix worked

# Linux
default-jdk --version 2>/dev/null || dpkg -s default-jdk | grep -i version
rpm -q default-jdk 2>/dev/null || true

# Windows
winget list | findstr /I "default-jdk"
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above BC-JAVA 1.80.2; BC-JAVA 1.81.1; BC-JAVA 1.84; BCPKIX-FIPS 2.0.11 (and 2 more SKUs, see vendor advisory). Restart any services that loaded the old library (systemctl restart <service> on Linux, restart the Windows service or reboot when prompted). For network appliances, run show version on the device and confirm the build matches the patched release.

Frequently asked questions

Related fixes

Other vulnerabilities in the same area that are worth patching alongside this one:

• How to Fix CVE-2026-7723: Missing Authentication in prefect , Missing Authentication in prefect
• How to Fix CVE-2026-24498: Information exposure in ipTIME T5008 , Information exposure in ipTIME T5008
• How to Fix CVE-2026-33485: SQL Injection in AVideo , SQL Injection in AVideo
• How to Fix CVE-2026-44448: Missing Authorization in erpnext , Missing Authorization in erpnext
• How to Fix CVE-2026-2248: Authentication Bypass in METIS WIC , Authentication Bypass in METIS WIC

Is CVE-2026-5588 actually being exploited?

According to the data sources above, no public confirmation of in-the-wild exploitation at this time. Either way, the fix is the same: apply the vendor patch.

Do I need to reboot after patching?

For OS or kernel updates, yes. For most userland packages a systemctl restart <service> is enough. Any process that loaded the old shared library keeps using it until restarted, so when in doubt, reboot.

What is the CVSS score?

6.3 (medium). Refer to the vendor advisory for the exact vector string.

Where is the official advisory?

See the References section at the bottom of this page; the vendor's URL is the authoritative source for affected builds and patched versions.

References

• Official vendor advisory: https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%905588
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5588
• https://github.com/bcgit/bc-java/commit/656bae0dbd9b1521f840521ff786e78749fe3057

*Written by Sai Kiran Pandrala. Assembled from the official vendor advisory, NVD record, and CISA KEV listing on 2026-05-25. Always confirm against the vendor's advisory before applying changes in production.*