fza_probe. The manipulation leads to use after free.This vulnerability is traded as CVE-2021-47306. The attack needs to be initiated within the local network. There is no exploit available.
It is recommended to upgrade the affected component.
Intelligence View
A vulnerability classified as critical has been found in Linux Kernel up to 5.4.134/5.10.52/5.13.4. Affected is the function fza_probe. The manipulation leads to use after free. This vulnerability is traded as CVE-2021-47306. The attack…
fza_probe. The manipulation leads to use after free.title: Detect Exploitation - CVE-2021-47306 | Linux Kernel up to 5.4.134/5.10.52/5.13.4 fza_probe use after free
id: b4b061fd-62f7-40b2-86d8-c6a5804926bc
status: experimental
description: Automatisch generierte SIEM-Erkennungsregel basierend auf CTI Intelligence
references:
- https://tsecurity.de/
author: iShareStuff CTI Automated Detection Engine
date: 2026-09-25
logsource:
category: network_connection
product: any
detection:
selection:
CommandLine|contains:
- 'exploit'
condition: selection
falsepositives:
- Legitime administrative Zugriffe oder Penetrationstests
level: high
tags:
- attack.initial_accessrule CTI_Threat_Indicator {
meta:
author = "iShareStuff CTI Automated Detection Engine"
date = "2026-09-25"
description = "YARA Signature for "
strings:
$str = "CVE-2021-47306 | Linux Kernel " ascii wide
condition:
any of them
}index=security sourcetype IN ("cisco:asa", "pan:traffic", "zeek_conn", "suricata", "WinEventLog:Security")
("CVE-2021-47306 Linux Kernel up to 54134")
| stats count earliest(_time) as first_seen latest(_time) as last_seen by src_ip, dest_ip, dest_host, signature
| eval first_seen=strftime(first_seen, "%Y-%m-%d %H:%M:%S"), last_seen=strftime(last_seen, "%Y-%m-%d %H:%M:%S")
| sort - countmessage: "*CVE-2021-47306 Linux Kernel up to 54134*"CommonSecurityLog
| where Message has "CVE-2021-47306 Linux Kernel up to 54134"
| summarize EventCount = count(), FirstSeen = min(TimeGenerated), LastSeen = max(TimeGenerated) by SourceIP, DestinationIP, DestinationPort, Activity
| extend DetectionRule = "iShareStuff-CTI-Compiled"
| sort by EventCount desc#!/usr/bin/env bash
# ==============================================================================
# iShareStuff CTI Fleet Remediation Automation
# Advisory Reference : CVE-2021-47306
# Target Ecosystem : Linux
# Generated Timestamp : 2026-09-24 23:43:50 UTC
# Execution Context : Run as root / privileged administrator
# ==============================================================================
set -euo pipefail
IFS=$'\n\t'
echo "[+] Starting automated remediation for advisory: CVE-2021-47306"
echo "[*] Detecting target host package manager..."
if command -v apt-get >/dev/null 2>&1; then
echo "[*] Debian/Ubuntu detected. Refreshing APT cache and patching security updates..."
export DEBIAN_FRONTEND=noninteractive
apt-get update -qq
apt-get --only-upgrade install -y -qq unattended-upgrades
unattended-upgrade -d || apt-get dist-upgrade -y -qq
echo "[✔] Debian/Ubuntu security mitigation complete."
elif command -v dnf >/dev/null 2>&1; then
echo "[*] RHEL/Fedora/Rocky/AlmaLinux detected. Applying security advisories via DNF..."
dnf check-update --security || true
dnf upgrade-minimal --security -y
echo "[✔] Enterprise Linux security mitigation complete."
elif command -v zypper >/dev/null 2>&1; then
echo "[*] SUSE/openSUSE detected. Applying security patches via Zypper..."
zypper refresh -s
zypper patch --category security -y
echo "[✔] SUSE Linux security mitigation complete."
elif command -v apk >/dev/null 2>&1; then
echo "[*] Alpine Linux detected. Upgrading base security packages..."
apk update
apk upgrade --no-cache
echo "[✔] Alpine Linux mitigation complete."
else
echo "[-] Unknown package manager. Please verify vendor patches manually for CVE-2021-47306." >&2
exit 1
fi
echo "[✔] Remediation procedure for CVE-2021-47306 executed successfully."
exit 0
<#
.SYNOPSIS
iShareStuff CTI Fleet Remediation Automation for CVE-2021-47306
.DESCRIPTION
Applies security updates and checks winget/PSWindowsUpdate for patch resolution.
Target: Linux | Generated: 2026-09-24 23:43:50 UTC
#>
#Requires -RunAsAdministrator
[CmdletBinding()]
param(
[switch]$DryRun = $false
)
Write-Host "[+] Initiating Fleet Security Patch for CVE-2021-47306..." -ForegroundColor Cyan
# 1. Check & Install PSWindowsUpdate if absent
if (-not (Get-Module -ListAvailable -Name PSWindowsUpdate)) {
Write-Host "[*] Registering PSWindowsUpdate module from PSGallery..." -ForegroundColor Yellow
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Install-PackageProvider -Name NuGet -MinimumVersion 2.8.5.201 -Force | Out-Null
Install-Module -Name PSWindowsUpdate -Force -Confirm:$false | Out-Null
}
# 2. Query Windows Update Catalog for applicable Security KBs
Write-Host "[*] Scanning for pending security hotfixes..." -ForegroundColor Gray
Import-Module PSWindowsUpdate -Force
if ($DryRun) {
Get-WUList -MicrosoftUpdate
Write-Host "[!] DryRun active: No changes applied." -ForegroundColor Yellow
exit 0
}
# 3. Apply Security KBs without uncontrolled reboot
try {
Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot -Verbose
Write-Host "[✔] Windows Update security rollups successfully deployed." -ForegroundColor Green
} catch {
Write-Warning "[-] Windows Update failed or returned pending reboot: $_"
}
# 4. Optional Winget Userland Upgrade Check
if (Get-Command winget.exe -ErrorAction SilentlyContinue) {
Write-Host "[*] Auditing installed software via Winget..." -ForegroundColor Gray
winget upgrade --all --accept-package-agreements --accept-source-agreements --silent || true
}
Write-Host "[✔] Host remediation audit completed for CVE-2021-47306." -ForegroundColor Green
---
# ==============================================================================
# iShareStuff CTI Multi-OS Fleet Remediation Playbook
# Advisory Reference : CVE-2021-47306
# Target Infrastructure : Linux
# Timestamp : 2026-09-24 23:43:50 UTC
# ==============================================================================
- name: "CTI Remediation Playbook for CVE-2021-47306"
hosts: all
become: true
gather_facts: true
tasks:
- name: "Log remediation initiation for CVE-2021-47306"
ansible.builtin.debug:
msg: "Executing automated patch mitigation for advisory CVE-2021-47306 on {{ inventory_hostname }}"
# Debian & Ubuntu Automation
- name: "Update apt cache and install security updates (Debian/Ubuntu)"
ansible.builtin.apt:
upgrade: dist
update_cache: yes
autoremove: yes
when: ansible_os_family == "Debian"
# RedHat / CentOS / Alma / Rocky Automation
- name: "Apply all security errata via DNF/YUM (Enterprise Linux)"
ansible.builtin.dnf:
name: "*"
state: latest
security: yes
when: ansible_os_family == "RedHat"
# SUSE Linux Automation
- name: "Apply security patches via Zypper (SUSE)"
community.general.zypper:
type: patch
category: security
state: latest
when: ansible_os_family == "Suse"
# Windows Fleet Automation
- name: "Install critical and security Windows Updates"
ansible.windows.win_updates:
category_names:
- SecurityUpdates
- CriticalUpdates
- UpdateRollups
state: installed
when: ansible_os_family == "Windows"
- name: "Record audit completion timestamp"
ansible.builtin.file:
path: "/var/log/isharestuff_cti_CVE-2021-47306.remediated"
state: touch
mode: "0640"
when: ansible_os_family != "Windows"
#!/usr/sbin/nft -f
# ISS-ZeroTrust Quarantine Policy for CVE-2021-47306
table inet iss_quarantine {
chain inbound_lockdown {
type filter hook input priority -10; policy drop;
# Allow established connections & loopback
ct state established,related accept
iif "lo" accept
# Whitelist SOC / Bastion Management Subnet
ip saddr 10.0.0.0/8 accept
ip saddr 192.168.1.0/24 accept
# Explicitly log & drop vulnerable service traffic
tcp dport 443 log prefix "[ISS-QUARANTINE-CVE-2021-47306] " drop
}
}apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: quarantine-CVE-2021-47306
namespace: production
labels:
security.isharestuff.com/quarantine: "true"
cve.mitigation/id: "CVE-2021-47306"
spec:
podSelector:
matchLabels:
app.kubernetes.io/vulnerable-cve: "CVE-2021-47306"
policyTypes:
- Ingress
- Egress
ingress:
# Restrict ingress solely to authorized security scanners & bastion pods
- from:
- namespaceSelector:
matchLabels:
kubernetes.io/metadata.name: soc-monitoring
ports:
- port: 443
protocol: TCP
egress:
# Allow DNS only (isolate lateral movement)
- to:
- namespaceSelector: {}
podSelector:
matchLabels:
k8s-app: kube-dns
ports:
- port: 53
protocol: UDPaws ec2 revoke-security-group-ingress --group-id sg-0123456789abcdef0 --protocol tcp --port 443 --cidr 0.0.0.0/0
(http.request.uri.path contains "CVE-2021-47306" or http.request.body.mime contains "exploit" or cf.threat_score gt 20)
Kognitive Analyse für identifizierte Bedrohung: Erhöhte Bedrohungslage im Bereich CVE-2021-47306 | Linux Kernel up to 5.4..... Basierend auf 368k Vektor-Korrelationen werden sofortige Isolationsmaßnahmen für betroffene Endpunkte empfohlen.
Netzwerk/Remote-Zugriff ohne Vorauthentifizierung möglich.
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