high CVSS 7.8 EPSS <0.1%

CVE-2024-26961·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: mac802154: fix llsec key resources release in mac802154_llsec_key_del mac802154_llsec_key_del() can free resources of a key directly without following the RCU rules for waiting before the end of a grace period. This may lead to use-after-free in case llsec_lookup_key() is traversing the list of keys in parallel with a key deletion: refcount_t: addition on 0; use-after-free. WARNING: CPU: 4 PID: 16000 at lib/refcount.c:25 refcount_warn_saturate+0x162/0x2a0 Modules linked in: CPU: 4 PID: 16000 Comm: wpan-ping Not tainted 6.7.0 #19 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x162/0x2a0 Call Trace: <TASK> llsec_lookup_key.isra.0+0x890/0x9e0 mac802154_llsec_encrypt+0x30c/0x9c0 ieee802154_subif_start_xmit+0x24/0x1e0 dev_hard_start_xmit+0x13e/0x690 sch_direct_xmit+0x2ae/0xbc0 __dev_queue_xmit+0x11dd/0x3c20 dgram_sendmsg+0x90b/0xd60 __sys_sendto+0x466/0x4c0 __x64_sys_sendto+0xe0/0x1c0 do_syscall_64+0x45/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 Also, ieee802154_llsec_key_entry structures are not freed by mac802154_llsec_key_del(): unreferenced object 0xffff8880613b6980 (size 64): comm "iwpan", pid 2176, jiffies 4294761134 (age 60.475s) hex dump (first 32 bytes): 78 0d 8f 18 80 88 ff ff 22 01 00 00 00 00 ad de x......."....... 00 00 00 00 00 00 00 00 03 00 cd ab 00 00 00 00 ................ backtrace: [<ffffffff81dcfa62>] __kmem_cache_alloc_node+0x1e2/0x2d0 [<ffffffff81c43865>] kmalloc_trace+0x25/0xc0 [<ffffffff88968b09>] mac802154_llsec_key_add+0xac9/0xcf0 [<ffffffff8896e41a>] ieee802154_add_llsec_key+0x5a/0x80 [<ffffffff8892adc6>] nl802154_add_llsec_key+0x426/0x5b0 [<ffffffff86ff293e>] genl_family_rcv_msg_doit+0x1fe/0x2f0 [<ffffffff86ff46d1>] genl_rcv_msg+0x531/0x7d0 [<ffffffff86fee7a9>] netlink_rcv_skb+0x169/0x440 [<ffffffff86ff1d88>] genl_rcv+0x28/0x40 [<ffffffff86fec15c>] netlink_unicast+0x53c/0x820 [<ffffffff86fecd8b>] netlink_sendmsg+0x93b/0xe60 [<ffffffff86b91b35>] ____sys_sendmsg+0xac5/0xca0 [<ffffffff86b9c3dd>] ___sys_sendmsg+0x11d/0x1c0 [<ffffffff86b9c65a>] __sys_sendmsg+0xfa/0x1d0 [<ffffffff88eadbf5>] do_syscall_64+0x45/0xf0 [<ffffffff890000ea>] entry_SYSCALL_64_after_hwframe+0x6e/0x76 Handle the proper resource release in the RCU callback function mac802154_llsec_key_del_rcu(). Note that if llsec_lookup_key() finds a key, it gets a refcount via llsec_key_get() and locally copies key id from key_entry (which is a list element). So it's safe to call llsec_key_put() and free the list entry after the RCU grace period elapses. Found by Linux Verification Center (linuxtesting.org).

Severity
high
Software
Kernel
Fixed in
6.8.3
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 1% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2024-26961 scores 7.8 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.8

Until: 6.8.3

Fixed in: 6.8.3

How to fix this CVE

Update your Linux kernel to version 6.8.3 or later to resolve a critical use-after-free vulnerability in the MAC 802.15.4 link-layer security key deletion function. This vulnerability allows concurrent access to freed memory when keys are deleted while being looked up, potentially causing kernel crashes or memory corruption. Apply the patch immediately if you are running kernel versions 6.8 through 6.8.2.

sudo dnf check-update kernel && sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your kernel version: uname -r — confirm if it is between 6.8.0 and 6.8.2 (vulnerable range)
  2. Verify if 802.15.4 WPAN (Wireless Personal Area Network) is active: lsmod | grep mac802154 — if no output, the vulnerable component is not loaded
  3. Search kernel logs for refcount warnings: dmesg | grep -i 'refcount_t: addition on 0' or journalctl -b | grep -i refcount — these indicate exploitation attempts
  4. After patching, confirm the new kernel version: uname -r — should show 6.8.3 or later, and verify module reload: modprobe -r mac802154 && modprobe mac802154

FAQ

What is CVE-2024-26961?

CVE-2024-26961 is a use-after-free vulnerability in the Linux kernel's MAC 802.15.4 link-layer security implementation where the key deletion function fails to properly synchronize with RCU (Read-Copy-Update), allowing freed memory to be accessed by concurrent key lookup operations.

Is CVE-2024-26961 being actively exploited?

No, CVE-2024-26961 is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog and there are no public exploits available. However, it can be triggered locally by an unprivileged user with access to 802.15.4 network interfaces.

What versions of Kernel are affected by CVE-2024-26961?

Linux kernel versions 6.8.0 through 6.8.2 are affected. The vulnerability was fixed in kernel 6.8.3 and later releases.

How do I check if my server is vulnerable to CVE-2024-26961?

Run 'uname -r' and check if the kernel version is 6.8.0, 6.8.1, or 6.8.2. Additionally, verify if MAC 802.15.4 support is enabled with 'grep -i 802154 /boot/config-$(uname -r)' or 'lsmod | grep mac802154'.

Does Defensia detect CVE-2024-26961?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2024-26961 will appear in your dashboard with remediation steps.

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References

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