CyberSecBulletin
CVE-2024-26865NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2024-26865 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 9905a157048f441f1412e7bd13372f4a971d75c6, f901ee07853ce97e9f1104c7c898fbbe447f0279, 9ceac040506a05a30b104b2aa2e9146810704500 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.23% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 9905a157048f441f1412e7bd13372f4a971d75c6 or f901ee07853ce97e9f1104c7c898fbbe447f0279 or 9ceac040506a05a30b104b2aa2e9146810704500 or 1e9fd5cf8d7f487332560f7bb312fc7d416817f3, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.83 or 6.6.23 or 6.7.11 or 6.8.2, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux467fa15356acfb7b2efa38839c3e76caa4e6e0ea up to, but not including, 9905a157048f441f1412e7bd13372f4a971d75c6; 467fa15356acfb7b2efa38839c3e76caa4e6e0ea up to, but not including, f901ee07853ce97e9f1104c7c898fbbe447f0279; 467fa15356acfb7b2efa38839c3e76caa4e6e0ea up to, but not including, 9ceac040506a05a30b104b2aa2e9146810704500; 467fa15356acfb7b2efa38839c3e76caa4e6e0ea up to, but not including, 1e9fd5cf8d7f487332560f7bb312fc7d416817f3; 467fa15356acfb7b2efa38839c3e76caa4e6e0ea up to, but not including, 2a750d6a5b365265dbda33330a6188547ddb5c24; 4.39905a157048f441f1412e7bd13372f4a971d75c6, f901ee07853ce97e9f1104c7c898fbbe447f0279, 9ceac040506a05a30b104b2aa2e9146810704500, 1e9fd5cf8d7f487332560f7bb312fc7d416817f3, 2a750d6a5b365265dbda33330a6188547ddb5c24
LinuxLinux Kernel4.3 up to, but not including, 6.1.83; 6.2 up to, but not including, 6.6.23; 6.7 up to, but not including, 6.7.11; 6.8 up to, but not including, 6.8.26.1.83, 6.6.23, 6.7.11, 6.8.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: rds: tcp: Fix use-after-free of net in reqsk_timer_handler(). syzkaller reported a warning of netns tracker [0] followed by KASAN splat [1] and another ref tracker warning [1]. syzkaller could not find a repro, but in the log, the only suspicious sequence was as follows: 18:26:22 executing program 1: r0 = socket$inet6_mptcp(0xa, 0x1, 0x106) ... connect$inet6(r0, &(0x7f0000000080)={0xa, 0x4001, 0x0, @loopback}, 0x1c) (async) The notable thing here is 0x4001 in connect(), which is RDS_TCP_PORT. So, the scenario would be: 1. unshare(CLONE_NEWNET) creates a per netns tcp listener in rds_tcp_listen_init(). 2. syz-executor connect()s to it and creates a reqsk. 3. syz-executor exit()s immediately. 4. netns is dismantled. [0] 5. reqsk timer is fired, and UAF happens while freeing reqsk. [1] 6. listener is freed after RCU grace period. [2] Basically, reqsk assumes that the listener guarantees netns safety until all reqsk timers are expired by holding the listener's refcount. However, this was not the case for kernel sockets. Commit 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in inet_twsk_purge()") fixed this issue only for per-netns ehash. Let's apply the same fix for the global ehash. [0]: ref_tracker: net notrefcnt@0000000065449cc3 has 1/1 users at sk_alloc (./include/net/net_namespace.h:337 net/core/sock.c:2146) inet6_create (net/ipv6/af_inet6.c:192 net/ipv6/af_inet6.c:119) __sock_create (net/socket.c:1572) rds_tcp_listen_init (net/rds/tcp_listen.c:279) rds_tcp_init_net (net/rds/tcp.c:577) ops_init (net/core/net_namespace.c:137) setup_net (net/core/net_namespace.c:340) copy_net_ns (net/core/net_namespace.c:497) create_new_namespaces (kernel/nsproxy.c:110) unshare_nsproxy_namespaces (kernel/nsproxy.c:228 (discriminator 4)) ksys_unshare (kernel/fork.c:3429) __x64_sys_unshare (kernel/fork.c:3496) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129) ... WARNING: CPU: 0 PID: 27 at lib/ref_tracker.c:179 ref_tracker_dir_exit (lib/ref_tracker.c:179) [1]: BUG: KASAN: slab-use-after-free in inet_csk_reqsk_queue_drop (./include/net/inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966) Read of size 8 at addr ffff88801b370400 by task swapper/0/0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1)) print_report (mm/kasan/report.c:378 mm/kasan/report.c:488) kasan_report (mm/kasan/report.c:603) inet_csk_reqsk_queue_drop (./include/net/inet_hashtables.h:180 net/ipv4/inet_connection_sock.c:952 net/ipv4/inet_connection_sock.c:966) reqsk_timer_handler (net/ipv4/inet_connection_sock.c:979 net/ipv4/inet_connection_sock.c:1092) call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701) __run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2038) run_timer_softirq (kernel/time/timer.c:2053) __do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:554) irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632 kernel/softirq.c:644) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1076 (discriminator 14)) </IRQ> Allocated by task 258 on cpu 0 at 83.612050s: kasan_save_stack (mm/kasan/common.c:48) kasan_save_track (mm/kasan/common.c:68) __kasan_slab_alloc (mm/kasan/common.c:343) kmem_cache_alloc (mm/slub.c:3813 mm/slub.c:3860 mm/slub.c:3867) copy_net_ns (./include/linux/slab.h:701 net/core/net_namespace.c:421 net/core/net_namespace.c:480) create_new_namespaces (kernel/nsproxy.c:110) unshare_nsproxy_name ---truncated---

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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