CVE-2026-31431: Local Kernel Privilege Escalation Vulnerability in Barracuda CloudGen Access Virtual Appliance

Published: 2026-05-01
Affected Product: Barracuda CloudGen Access Virtual Appliance v1.1.0 and earlier (Ubuntu-based OVA)

Summary

A critical local privilege escalation vulnerability (CVE-2026-31431, "Copy Fail") has been disclosed affecting the Linux kernel. This vulnerability allows any unprivileged local user to gain root access with 100% reliability through a logic flaw in the kernel's AF_ALG crypto socket interface (algif_aead module).

All Barracuda CloudGen Access virtual Appliance deployments v1.1.0 and earlier running on the Ubuntu-based OVA image are affected.

Impact

An attacker with local access to the virtual appliance, or who achieves code execution through a service running on the virtual appliance, can escalate to root privileges. This could allow complete compromise of the CGA virtual appliance, including access to proxy and connector configurations, certificates, and network traffic.

The exploit operates through the kernel page cache and leaves no trace on disk, making forensic detection difficult.

Affected Versions

Barracuda CloudGen Access virtual appliance v1.1.0 and earlier (Ubuntu-based OVA).

Required Action

Option 1: kmod Package Update (Recommended — Ubuntu's Official Fix)

Ubuntu has released a fix in the kmod package. For Ubuntu 22.04 (Jammy), the fixed version is 29-1ubuntu1.1:

sudo apt-get update
sudo apt-get upgrade -y kmod

No reboot is required if the algif_aead module is not currently loaded (which is the case on most systems).

Option 2: Manual Module Blacklist (Immediate Mitigation)

If the kmod update cannot be applied immediately, block the vulnerable module manually:

echo "install algif_aead /bin/false" | sudo tee /etc/modprobe.d/disable-algif-aead.conf
sudo rmmod algif_aead 2>/dev/null || true

The kmod update should still be applied at the next available maintenance window.

Impact of Mitigation

Disabling the algif_aead module does not affect:

CGA proxy or connector services
SSH, TLS, or VPN functionality
dm-crypt/LUKS disk encryption
Any standard cryptographic operations on the virtual appliance

Verification

After applying remediation:

# Check kmod package version (should be >= 29-1ubuntu1.1 for Ubuntu 22.04)
dpkg -l kmod | grep kmod

# Confirm vulnerable module is not loaded
lsmod | grep algif_aead
# Expected: no output (module not loaded)

# Check kernel version
uname -r

# NOTE: Some guides suggest checking /boot/config-* for commit a664bf3d603d.
# This does not work — /boot/config contains kernel build options, not commit hashes.
# The kmod version check above is the authoritative verification for Ubuntu 22.04.

Security Testing

Do NOT run public proof-of-concept exploits in production environments. Use test or staging environments to validate that remediation was applied correctly.

Contact

For questions regarding this advisory, contact Barracuda Networks Technical Support.

This advisory will be updated as additional information becomes available.