In IGEL OS before 11

CVE-2025-47827 is a Secure Boot bypass in the igel-flash-driver Linux kernel module shipped with IGEL OS 10 (all versions before OS 11). The module fails to verify the cryptographic signature of the SquashFS root filesystem it mounts during boot. An attacker with physical access can chain through the Microsoft 3rd Party UEFI CA → IGEL-signed GRUB → IGEL-signed vulnerable kernel, then swap in a completely untrusted root filesystem—or use kexec_load to replace the running kernel entirely. The result is a full Secure Boot chain-of-trust collapse: kernel-level rootkits, credential harvesting from VDI sessions, EFI variable persistence across reboots, and anti-forensic cloaking. A public PoC from researcher Zack Didcott demonstrates the complete chain from ISO extraction to bootable malicious image.

The vendor scored this CVSS 4.6 MEDIUM with a vector of AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. That impact triad is plainly wrong: a Secure Boot bypass that enables arbitrary kernel loading and rootkit persistence is not 'no confidentiality impact, no integrity impact.' A corrected vector with C:H/I:H/A:H and AV:P yields 6.8. More importantly, IGEL OS 10 is end-of-life with no patch available—the only remediation is migration to OS 11 or OS 12. CISA added this to KEV on 2025-10-14, confirming active exploitation in the wild despite the physical-access requirement. The vendor severity understates the real risk for any organization still running IGEL OS 10 thin clients in semi-public environments like hospital nursing stations, retail kiosks, or call center floors.

1. Apply Microsoft DBX revocation immediately — Install the UEFI Secure Boot DBX update version 20250902 or later (released 2025-10-20) on all devices that have ever booted IGEL OS 10. This revokes the vulnerable IGEL shim signatures, preventing the boot chain from loading even if the crafted media is present. Deploy within 3 days per the noisgate mitigation SLA for KEV-listed vulnerabilities—treat as immediate due to active exploitation.
2. Migrate all IGEL OS 10 devices to OS 11 or OS 12 — IGEL OS 10 is end-of-life with zero security support. The only remediation is OS migration. Prioritize devices in physically accessible locations (healthcare, retail, shared workspaces). Target completion within 30 days per the noisgate remediation SLA for HIGH severity. Use IGEL UMS to inventory and schedule firmware pushes.
3. Add vulnerable kernel and shim hashes to DBX/MOKX deny lists — If the Microsoft DBX update cannot be applied uniformly (e.g., devices not managed via WSUS/Intune), manually add the SHA-256 hashes of the vulnerable bootx64.efi, igelx64.efi, and bzImage binaries to local DBX or MOKX deny lists. Hashes are published in the PoC repository.
4. Enforce BIOS boot-order locks and USB boot disablement — Configure BIOS/UEFI settings to disable USB boot and lock boot order with a supervisor password. This does not fix the vulnerability (an attacker with physical access and time can reset CMOS or write to internal storage), but it raises the bar for opportunistic exploitation. Deploy within 3 days on all IGEL OS 10 endpoints.
5. Segment thin client VLANs with NDR monitoring — Place thin clients on dedicated VLANs with network detection and response (NDR) monitoring for anomalous outbound traffic. A rootkited thin client must exfiltrate credentials over the network—NDR can catch the C2 channel even when endpoint detection is blinded. Verify VLAN segmentation and NDR coverage within 3 days.
6. Implement TPM-based remote attestation where hardware supports it — For devices with TPM 2.0, configure measured boot with remote attestation to detect tampered boot chains. This is a detection control, not prevention, but it provides visibility that Secure Boot alone no longer offers on compromised IGEL OS 10 devices.

Run this script on each IGEL thin client endpoint (or push via IGEL UMS custom command). Requires root. Example: sudo bash check_cve_2025_47827.sh. It checks for IGEL OS 10 and the presence of the vulnerable igel-flash-driver module.

#!/usr/bin/env bash
# check_cve_2025_47827.sh
# Checks whether this IGEL endpoint is vulnerable to CVE-2025-47827
# (Secure Boot bypass via igel-flash-driver signature verification flaw)
# Run as root on the IGEL thin client.
# Exit codes: 0 = VULNERABLE, 1 = PATCHED, 2 = UNKNOWN

set -euo pipefail

VULNERABLE=0
PATCHED=1
UNKNOWN=2

# Check if this is an IGEL system
if [ ! -f /etc/igel/os-release ] && [ ! -f /etc/os-release ]; then
  echo "UNKNOWN - Cannot determine OS. Not an IGEL device or os-release missing."
  exit $UNKNOWN
fi

# Try IGEL-specific release file first, fall back to standard
RELEASE_FILE="/etc/igel/os-release"
if [ ! -f "$RELEASE_FILE" ]; then
  RELEASE_FILE="/etc/os-release"
fi

# Check for IGEL OS identification
if ! grep -qi 'igel' "$RELEASE_FILE" 2>/dev/null; then
  echo "UNKNOWN - This does not appear to be an IGEL OS device."
  exit $UNKNOWN
fi

# Extract version - try multiple patterns
VERSION=""
if grep -qE 'VERSION_ID|FIRMWARE_VERSION' "$RELEASE_FILE" 2>/dev/null; then
  VERSION=$(grep -E 'VERSION_ID|FIRMWARE_VERSION' "$RELEASE_FILE" | head -1 | grep -oE '[0-9]+\.[0-9]+' | head -1)
fi

# Also check /config/os-runlevel or /etc/igel/version if available
if [ -z "$VERSION" ] && [ -f /etc/igel/version ]; then
  VERSION=$(cat /etc/igel/version | grep -oE '[0-9]+\.[0-9]+' | head -1)
fi

if [ -z "$VERSION" ]; then
  # Check if igel-flash-driver module is loaded as a fallback indicator
  if lsmod 2>/dev/null | grep -q 'igel_flash'; then
    echo "VULNERABLE - igel-flash-driver module is loaded (likely IGEL OS 10)."
    exit $VULNERABLE
  fi
  echo "UNKNOWN - Could not determine IGEL OS version."
  exit $UNKNOWN
fi

MAJOR=$(echo "$VERSION" | cut -d'.' -f1)

if [ "$MAJOR" -lt 11 ] 2>/dev/null; then
  echo "VULNERABLE - IGEL OS version $VERSION detected (< 11). CVE-2025-47827 applies."
  echo "  Action: Migrate to IGEL OS 11+ or OS 12. No patch exists for OS 10."
  exit $VULNERABLE
elif [ "$MAJOR" -ge 11 ] 2>/dev/null; then
  echo "PATCHED - IGEL OS version $VERSION detected (>= 11). Not affected by CVE-2025-47827."
  exit $PATCHED
else
  echo "UNKNOWN - Could not parse IGEL OS major version from '$VERSION'."
  exit $UNKNOWN
fi

1. IGEL ISN-2025-22 Advisory
2. PoC and Vulnerability Report (Zack Didcott)
3. CISA KEV Alert (2025-10-14)
4. SecurityOnline Technical Analysis
5. Tenable Plugin 282474
6. Help Net Security - October 2025 Patch Tuesday
7. NVD Entry
8. GitHub Advisory GHSA-pww7-j9v6-xc6j