CVE-2024-40910: Linux kernel · ax25: Fix refcount imbalance on inbound connections
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 8.8 High · fixed in 4.4.0-1141.147 : patch Linux kernel soon.
Data as of 12 Nov 2026, 19:04 UTC
- Patch
- Available – fixed in 4.4.0-1141.147, 4.15.0-1186.201~14.04.1, 4.4.0-266.300~14.04.1 +94
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 12 Jul 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-6999-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7004-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7005-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7008-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7005-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6999-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7029-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7173-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7173-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7179-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7179-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7186-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-ibmpkg:deb/ubuntu/linux-ibm?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: ax25: Fix refcount imbalance on inbound connections When releasing a socket in ax25_release(), we call netdev_put() to decrease the refcount on the associated ax.25 device. However, the execution path for accepting an incoming connection never calls netdev_hold(). This imbalance leads to refcount errors, and ultimately to kernel crashes. A typical call trace for the above situation will start with one of the following errors: refcount_t: decrement hit 0; leaking memory. refcount_t: underflow; use-after-free. And will then have a trace like: Call Trace: <TASK> ? show_regs+0x64/0x70 ? __warn+0x83/0x120 ? refcount_warn_saturate+0xb2/0x100 ? report_bug+0x158/0x190 ? prb_read_valid+0x20/0x30 ? handle_bug+0x3e/0x70 ? exc_invalid_op+0x1c/0x70 ? asm_exc_invalid_op+0x1f/0x30 ? refcount_warn_saturate+0xb2/0x100 ? refcount_warn_saturate+0xb2/0x100 ax25_release+0x2ad/0x360 __sock_release+0x35/0xa0 sock_close+0x19/0x20 [...] On reboot (or any attempt to remove the interface), the kernel gets stuck in an infinite loop: unregister_netdevice: waiting for ax0 to become free. Usage count = 0 This patch corrects these issues by ensuring that we call netdev_hold() and ax25_dev_hold() for new connections in ax25_accept(). This makes the logic leading to ax25_accept() match the logic for ax25_bind(): in both cases we increment the refcount, which is ultimately decremented in ax25_release().
References
- ubuntu.com/security/CVE-2024-40910 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-40910 (opens in a new tab)
- git.kernel.org/linus/3c34fb0bd4a4237592c5ecb5b2e2531900c55774 (opens in a new tab)
- ubuntu.com/security/notices/USN-6999-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7004-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7005-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7008-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7005-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6999-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7029-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7173-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7173-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7179-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7179-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7186-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7179-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7186-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7194-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7195-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7195-2 (opens in a new tab)