CVE-2025-21787
📋 TL;DR
A Linux kernel vulnerability in the team networking driver allows uninitialized memory disclosure when processing TEAM_OPTION_TYPE_STRING options. This affects systems using the team driver for network interface aggregation. Attackers could potentially leak kernel memory contents through specially crafted requests.
💻 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 →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 information disclosure leading to potential privilege escalation or system compromise through information leakage.
Likely Case
Information disclosure of uninitialized kernel memory, potentially revealing sensitive data or system state.
If Mitigated
Limited impact with proper network isolation and access controls preventing unauthorized access to team driver interfaces.
🎯 Exploit Status
Exploitation requires access to team driver management interfaces (typically via netlink). The vulnerability was discovered through syzkaller fuzzing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 4236bf4716589558cc0f3c3612642b2c2141b04e, 4512482e4805dd30bc77dec511f2a2edba5cb868, 5bef3ac184b5626ea62385d6b82a1992b89d7940, 7c30483d0f6bdb2230e10e3e4be5167927eac7a0, 7f5af50f3aa0af8cbef9fb76fffeed69e8143f59
Vendor Advisory: https://git.kernel.org/stable/c/4236bf4716589558cc0f3c3612642b2c2141b04e
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check with your distribution for specific kernel package updates. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable team driver module
linuxPrevent loading of the vulnerable team driver module
echo 'blacklist team' >> /etc/modprobe.d/blacklist-team.conf
rmmod team
Restrict netlink access
linuxLimit access to netlink sockets used by team driver
iptables -A OUTPUT -m owner --uid-owner root -j ACCEPT
iptables -A OUTPUT -d 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -j DROP
🧯 If You Can't Patch
- Disable team driver if not required for system functionality
- Implement strict network segmentation to limit access to team driver management interfaces
🔍 How to Verify
Check if Vulnerable:
Check if team module is loaded: lsmod | grep team. Check kernel version: uname -r and compare with patched versions.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to patched version and team module functions correctly if needed.📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing team driver errors or crashes
- Netlink connection attempts to team driver
Network Indicators:
- Unusual netlink socket activity
- Team driver configuration changes from unauthorized sources
SIEM Query:
source="kernel" AND "team" AND ("BUG" OR "KMSAN" OR "uninit-value")🔗 References
- https://git.kernel.org/stable/c/4236bf4716589558cc0f3c3612642b2c2141b04e
- https://git.kernel.org/stable/c/4512482e4805dd30bc77dec511f2a2edba5cb868
- https://git.kernel.org/stable/c/5bef3ac184b5626ea62385d6b82a1992b89d7940
- https://git.kernel.org/stable/c/7c30483d0f6bdb2230e10e3e4be5167927eac7a0
- https://git.kernel.org/stable/c/7f5af50f3aa0af8cbef9fb76fffeed69e8143f59
- https://git.kernel.org/stable/c/8401cade1918281177974b32c925afdce750d292
- https://git.kernel.org/stable/c/d071a91fa614ecdf760c29f61f6a7bfb7df796d6
- https://git.kernel.org/stable/c/f443687ad20c70320d1248f35f57bf46cac8df0a
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
