CVE-2025-21709
📋 TL;DR
A race condition vulnerability in the Linux kernel's memory management subsystem during process forking. If memory allocation fails during dup_mmap(), the partially initialized mm_struct can be accessed by other kernel components like uprobe, potentially causing kernel instability or crashes. Affects Linux systems with specific kernel versions.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic or system crash leading to denial of service, potentially allowing limited information disclosure through kernel memory access.
Likely Case
System instability, kernel oops, or process crashes when specific race conditions are triggered during process forking under memory pressure.
If Mitigated
Minimal impact as the race window is narrow and requires specific conditions; properly patched systems are protected.
🎯 Exploit Status
Exploitation requires triggering specific race conditions during process forking with memory pressure. Discovered by syzbot fuzzing, not known to be actively exploited.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel commits 64c37e134b120fb462fb4a80694bfb8e7be77b14 and da139948aeda677ac09cc0e7d837f8a314de7d55
Vendor Advisory: https://git.kernel.org/stable/c/64c37e134b120fb462fb4a80694bfb8e7be77b14
Restart Required: Yes
Instructions:
1. Update to a kernel version containing the fix. 2. Check your distribution's security advisories for backported patches. 3. Reboot the system after kernel update.
🔧 Temporary Workarounds
Limit process forking
linuxReduce likelihood of triggering the race condition by limiting process creation
ulimit -u [max_processes]
systemctl set-property [service_name] TasksMax=[value]
Memory pressure management
linuxMaintain sufficient available memory to reduce allocation failures during dup_mmap()
sysctl vm.overcommit_memory=2
sysctl vm.overcommit_ratio=80
🧯 If You Can't Patch
- Implement strict process creation controls and monitoring
- Ensure adequate system memory and implement memory pressure monitoring
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with distribution security advisories. Vulnerable if running kernel without the fix commits.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits: 64c37e134b120fb462fb4a80694bfb8e7be77b14 and da139948aeda677ac09cc0e7d837f8a314de7d55📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages related to mm_struct, uprobe, or dup_mmap
- Process crash logs during forking operations
- Memory allocation failure logs
Network Indicators:
- None - local vulnerability only
SIEM Query:
search 'kernel: BUG:' OR 'kernel: Oops:' OR 'kernel: general protection fault' near 'dup_mmap' OR 'uprobe' OR 'mm_struct'