CVE-2025-21734
📋 TL;DR
A memory corruption vulnerability in the Linux kernel's fastrpc driver allows attackers to pass improperly calculated page sizes when copying non-registered buffers. This could lead to out-of-bounds memory access and potential kernel memory issues. Systems running vulnerable Linux kernel versions with fastrpc driver enabled are affected.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Kernel memory corruption leading to privilege escalation, denial of service, or arbitrary code execution in kernel context.
Likely Case
Kernel panic or system crash causing denial of service.
If Mitigated
No impact if fastrpc driver is disabled or system is patched.
🎯 Exploit Status
Requires local access and ability to interact with fastrpc driver. Exploitation depends on specific memory layout and conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing the fix commits listed in references
Vendor Advisory: https://git.kernel.org/stable/c/24a79c6bc8de763f7c50f4f84f8b0c183bc25a51
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.
🔧 Temporary Workarounds
Disable fastrpc driver
allPrevent loading of vulnerable fastrpc kernel module
echo 'blacklist fastrpc' >> /etc/modprobe.d/blacklist.conf
rmmod fastrpc
🧯 If You Can't Patch
- Disable fastrpc driver module if not required
- Restrict local user access to systems with vulnerable kernel
🔍 How to Verify
Check if Vulnerable:
Check if fastrpc module is loaded: lsmod | grep fastrpc. If loaded and kernel version is vulnerable, system is at risk.Check Version:
uname -rVerify Fix Applied:
Check kernel version after update matches patched version from vendor. Verify fastrpc module loads without issues.📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- System crashes/panics
- dmesg errors related to fastrpc or memory corruption
Network Indicators:
- None - local vulnerability only
SIEM Query:
Search for kernel panic events or fastrpc-related errors in system logs🔗 References
- https://git.kernel.org/stable/c/24a79c6bc8de763f7c50f4f84f8b0c183bc25a51
- https://git.kernel.org/stable/c/c0464bad0e85fcd5d47e4297d1e410097c979e55
- https://git.kernel.org/stable/c/c3f7161123fcbdc64e90119ccce292d8b66281c4
- https://git.kernel.org/stable/c/c56ba3ea8e3c9a69a992aad18f7a65e43e51d623
- https://git.kernel.org/stable/c/e966eae72762ecfdbdb82627e2cda48845b9dd66
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
