VulnerabilityPublished 2 Apr 2024Updated 12 Nov 2026

CVE-2024-26676: Linux kernel · af_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1061.67~20.04.1 : update Linux kernel when convenient.

Data as of 12 Nov 2026, 18:50 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 5.15.0-1061.67~20.04.1, 5.15.0-1063.72~20.04.1, 5.15.0-1059.67~20.04.1 +38

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Apr 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Patches and advisories

Affected software

Product	Affected	Fixed in
Ubuntu Pro Realtime 24.04 LTSlinux-raspi-realtime`pkg:deb/ubuntu/linux-raspi-realtime?arch=source&distro=realtime/noble`Other threats	Affected <6.8.0-2001.1	Fixed in 6.8.0-2001.1
Ubuntu 22.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=jammy`Other threats	Affected <5.15.0-106.116	Fixed in 5.15.0-106.116
Ubuntu 22.04 LTSlinux-allwinner-5.19`pkg:deb/ubuntu/linux-allwinner-5.19?arch=source&distro=jammy`Other threats	Affected 5.19.0-1007.7~22.04.1 – 5.19.0-1015.15~22.04.1 8 affected builds	Fixed in–
Ubuntu 22.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=jammy`Other threats	Affected <5.15.0-1061.67	Fixed in 5.15.0-1061.67
Ubuntu 22.04 LTSlinux-aws-5.19`pkg:deb/ubuntu/linux-aws-5.19?arch=source&distro=jammy`Other threats	Affected 5.19.0-1019.20~22.04.1 – 5.19.0-1029.30~22.04.1 10 affected builds	Fixed in–
Ubuntu 22.04 LTSlinux-aws-6.2`pkg:deb/ubuntu/linux-aws-6.2?arch=source&distro=jammy`Other threats	Affected 6.2.0-1005.5~22.04.1 – 6.2.0-1018.18~22.04.1 14 affected builds	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: af_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC. syzbot reported a warning [0] in __unix_gc() with a repro, which creates a socketpair and sends one socket's fd to itself using the peer. socketpair(AF_UNIX, SOCK_STREAM, 0, [3, 4]) = 0 sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\360", iov_len=1}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, cmsg_data=[3]}], msg_controllen=24, msg_flags=0}, MSG_OOB|MSG_PROBE|MSG_DONTWAIT|MSG_ZEROCOPY) = 1 This forms a self-cyclic reference that GC should finally untangle but does not due to lack of MSG_OOB handling, resulting in memory leak. Recently, commit 11498715f266 ("af_unix: Remove io_uring code for GC.") removed io_uring's dead code in GC and revealed the problem. The code was executed at the final stage of GC and unconditionally moved all GC candidates from gc_candidates to gc_inflight_list. That papered over the reported problem by always making the following WARN_ON_ONCE(!list_empty(&gc_candidates)) false. The problem has been there since commit 2aab4b969002 ("af_unix: fix struct pid leaks in OOB support") added full scm support for MSG_OOB while fixing another bug. To fix this problem, we must call kfree_skb() for unix_sk(sk)->oob_skb if the socket still exists in gc_candidates after purging collected skb. Then, we need to set NULL to oob_skb before calling kfree_skb() because it calls last fput() and triggers unix_release_sock(), where we call duplicate kfree_skb(u->oob_skb) if not NULL. Note that the leaked socket remained being linked to a global list, so kmemleak also could not detect it. We need to check /proc/net/protocol to notice the unfreed socket. [0]: WARNING: CPU: 0 PID: 2863 at net/unix/garbage.c:345 __unix_gc+0xc74/0xe80 net/unix/garbage.c:345 Modules linked in: CPU: 0 PID: 2863 Comm: kworker/u4:11 Not tainted 6.8.0-rc1-syzkaller-00583-g1701940b1a02 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Workqueue: events_unbound __unix_gc RIP: 0010:__unix_gc+0xc74/0xe80 net/unix/garbage.c:345 Code: 8b 5c 24 50 e9 86 f8 ff ff e8 f8 e4 22 f8 31 d2 48 c7 c6 30 6a 69 89 4c 89 ef e8 97 ef ff ff e9 80 f9 ff ff e8 dd e4 22 f8 90 <0f> 0b 90 e9 7b fd ff ff 48 89 df e8 5c e7 7c f8 e9 d3 f8 ff ff e8 RSP: 0018:ffffc9000b03fba0 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffffc9000b03fc10 RCX: ffffffff816c493e RDX: ffff88802c02d940 RSI: ffffffff896982f3 RDI: ffffc9000b03fb30 RBP: ffffc9000b03fce0 R08: 0000000000000001 R09: fffff52001607f66 R10: 0000000000000003 R11: 0000000000000002 R12: dffffc0000000000 R13: ffffc9000b03fc10 R14: ffffc9000b03fc10 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005559c8677a60 CR3: 000000000d57a000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> process_one_work+0x889/0x15e0 kernel/workqueue.c:2633 process_scheduled_works kernel/workqueue.c:2706 [inline] worker_thread+0x8b9/0x12a0 kernel/workqueue.c:2787 kthread+0x2c6/0x3b0 kernel/kthread.c:388 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242 </TASK>

References

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