Linux: Use After Free
CVE-2024-40954 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 78e4aa528a7b1204219d808310524344f627d069, 893eeba94c40d513cd0fe6539330ebdaea208c0e, 454c454ed645fed051216b79622f7cb69c1638f5 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 0.26% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 78e4aa528a7b1204219d808310524344f627d069 or 893eeba94c40d513cd0fe6539330ebdaea208c0e or 454c454ed645fed051216b79622f7cb69c1638f5 or 5dfe2408fd7dc4d2e7ac38a116ff0a37b1cfd3b9, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.162 or 6.1.96 or 6.6.36 or 6.9.7, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | c5dbb89fc2ac013afe67b9e4fcb3743c02b567cd up to, but not including, 78e4aa528a7b1204219d808310524344f627d069; c5dbb89fc2ac013afe67b9e4fcb3743c02b567cd up to, but not including, 893eeba94c40d513cd0fe6539330ebdaea208c0e; c5dbb89fc2ac013afe67b9e4fcb3743c02b567cd up to, but not including, 454c454ed645fed051216b79622f7cb69c1638f5; c5dbb89fc2ac013afe67b9e4fcb3743c02b567cd up to, but not including, 5dfe2408fd7dc4d2e7ac38a116ff0a37b1cfd3b9; c5dbb89fc2ac013afe67b9e4fcb3743c02b567cd up to, but not including, 6cd4a78d962bebbaf8beb7d2ead3f34120e3f7b2; 5.12 | 78e4aa528a7b1204219d808310524344f627d069, 893eeba94c40d513cd0fe6539330ebdaea208c0e, 454c454ed645fed051216b79622f7cb69c1638f5, 5dfe2408fd7dc4d2e7ac38a116ff0a37b1cfd3b9, 6cd4a78d962bebbaf8beb7d2ead3f34120e3f7b2 |
| Linux | Linux Kernel | 5.12 up to, but not including, 5.15.162; 5.16 up to, but not including, 6.1.96; 6.2 up to, but not including, 6.6.36; 6.7 up to, but not including, 6.9.7; 6.10 | 5.15.162, 6.1.96, 6.6.36, 6.9.7 |
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 system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: net: do not leave a dangling sk pointer, when socket creation fails It is possible to trigger a use-after-free by: * attaching an fentry probe to __sock_release() and the probe calling the bpf_get_socket_cookie() helper * running traceroute -I 1.1.1.1 on a freshly booted VM A KASAN enabled kernel will log something like below (decoded and stripped): ================================================================== BUG: KASAN: slab-use-after-free in __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29) Read of size 8 at addr ffff888007110dd8 by task traceroute/299 CPU: 2 PID: 299 Comm: traceroute Tainted: G E 6.10.0-rc2+ #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:117 (discriminator 1)) print_report (mm/kasan/report.c:378 mm/kasan/report.c:488) ? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29) kasan_report (mm/kasan/report.c:603) ? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29) kasan_check_range (mm/kasan/generic.c:183 mm/kasan/generic.c:189) __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29) bpf_get_socket_ptr_cookie (./arch/x86/include/asm/preempt.h:94 ./include/linux/sock_diag.h:42 net/core/filter.c:5094 net/core/filter.c:5092) bpf_prog_875642cf11f1d139___sock_release+0x6e/0x8e bpf_trampoline_6442506592+0x47/0xaf __sock_release (net/socket.c:652) __sock_create (net/socket.c:1601) ... Allocated by task 299 on cpu 2 at 78.328492s: kasan_save_stack (mm/kasan/common.c:48) kasan_save_track (mm/kasan/common.c:68) __kasan_slab_alloc (mm/kasan/common.c:312 mm/kasan/common.c:338) kmem_cache_alloc_noprof (mm/slub.c:3941 mm/slub.c:4000 mm/slub.c:4007) sk_prot_alloc (net/core/sock.c:2075) sk_alloc (net/core/sock.c:2134) inet_create (net/ipv4/af_inet.c:327 net/ipv4/af_inet.c:252) __sock_create (net/socket.c:1572) __sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706) __x64_sys_socket (net/socket.c:1718) 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:130) Freed by task 299 on cpu 2 at 78.328502s: kasan_save_stack (mm/kasan/common.c:48) kasan_save_track (mm/kasan/common.c:68) kasan_save_free_info (mm/kasan/generic.c:582) poison_slab_object (mm/kasan/common.c:242) __kasan_slab_free (mm/kasan/common.c:256) kmem_cache_free (mm/slub.c:4437 mm/slub.c:4511) __sk_destruct (net/core/sock.c:2117 net/core/sock.c:2208) inet_create (net/ipv4/af_inet.c:397 net/ipv4/af_inet.c:252) __sock_create (net/socket.c:1572) __sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706) __x64_sys_socket (net/socket.c:1718) 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:130) Fix this by clearing the struct socket reference in sk_common_release() to cover all protocol families create functions, which may already attached the reference to the sk object with sock_init_data().
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.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/454c454ed645fed051216b79622f7cb69c1638f5
- git.kernel.org/stable/c/5dfe2408fd7dc4d2e7ac38a116ff0a37b1cfd3b9
- git.kernel.org/stable/c/6cd4a78d962bebbaf8beb7d2ead3f34120e3f7b2
- git.kernel.org/stable/c/78e4aa528a7b1204219d808310524344f627d069
- git.kernel.org/stable/c/893eeba94c40d513cd0fe6539330ebdaea208c0e
Other references
Recent Use After Free vulnerabilities
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