Linux: Use After Free
CVE-2022-48956 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 b3d7ff8c04a83279fb7641fc4d5aa82a602df7c0, 7e0dcd5f3ade221a6126278aca60c8ab4cc3bce9, 6b6d3be3661bff2746cab26147bd629aa034e094 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 0.27% 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 b3d7ff8c04a83279fb7641fc4d5aa82a602df7c0 or 7e0dcd5f3ade221a6126278aca60c8ab4cc3bce9 or 6b6d3be3661bff2746cab26147bd629aa034e094 or 8208d7e56b1e579320b9ff3712739ad2e63e1f86, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.14.302 or 4.19.269 or 5.4.227 or 5.10.159, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, b3d7ff8c04a83279fb7641fc4d5aa82a602df7c0; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 7e0dcd5f3ade221a6126278aca60c8ab4cc3bce9; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 6b6d3be3661bff2746cab26147bd629aa034e094; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 8208d7e56b1e579320b9ff3712739ad2e63e1f86; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 7390c70bd431cbfa6951477e2c80a301643e284b; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 9b1a468a455d8319041528778d0e684a4c062792; 1758fd4688eb92c796e75bdb1d256dc558ef9581 up to, but not including, 803e84867de59a1e5d126666d25eb4860cfd2ebe; 4.13 | b3d7ff8c04a83279fb7641fc4d5aa82a602df7c0, 7e0dcd5f3ade221a6126278aca60c8ab4cc3bce9, 6b6d3be3661bff2746cab26147bd629aa034e094, 8208d7e56b1e579320b9ff3712739ad2e63e1f86, 7390c70bd431cbfa6951477e2c80a301643e284b, 9b1a468a455d8319041528778d0e684a4c062792 |
| Linux | Linux Kernel | 4.13 up to, but not including, 4.14.302; 4.15 up to, but not including, 4.19.269; 4.20 up to, but not including, 5.4.227; 5.5 up to, but not including, 5.10.159; 5.11 up to, but not including, 5.15.83; 5.16 up to, but not including, 6.0.13; 6.1 | 4.14.302, 4.19.269, 5.4.227, 5.10.159, 5.15.83, 6.0.13 |
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: ipv6: avoid use-after-free in ip6_fragment() Blamed commit claimed rcu_read_lock() was held by ip6_fragment() callers. It seems to not be always true, at least for UDP stack. syzbot reported: BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:245 [inline] BUG: KASAN: use-after-free in ip6_fragment+0x2724/0x2770 net/ipv6/ip6_output.c:951 Read of size 8 at addr ffff88801d403e80 by task syz-executor.3/7618 CPU: 1 PID: 7618 Comm: syz-executor.3 Not tainted 6.1.0-rc6-syzkaller-00012-g4312098baf37 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x15e/0x45d mm/kasan/report.c:395 kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 ip6_dst_idev include/net/ip6_fib.h:245 [inline] ip6_fragment+0x2724/0x2770 net/ipv6/ip6_output.c:951 __ip6_finish_output net/ipv6/ip6_output.c:193 [inline] ip6_finish_output+0x9a3/0x1170 net/ipv6/ip6_output.c:206 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip6_output+0x1f1/0x540 net/ipv6/ip6_output.c:227 dst_output include/net/dst.h:445 [inline] ip6_local_out+0xb3/0x1a0 net/ipv6/output_core.c:161 ip6_send_skb+0xbb/0x340 net/ipv6/ip6_output.c:1966 udp_v6_send_skb+0x82a/0x18a0 net/ipv6/udp.c:1286 udp_v6_push_pending_frames+0x140/0x200 net/ipv6/udp.c:1313 udpv6_sendmsg+0x18da/0x2c80 net/ipv6/udp.c:1606 inet6_sendmsg+0x9d/0xe0 net/ipv6/af_inet6.c:665 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg+0xd3/0x120 net/socket.c:734 sock_write_iter+0x295/0x3d0 net/socket.c:1108 call_write_iter include/linux/fs.h:2191 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ed/0xdd0 fs/read_write.c:584 ksys_write+0x1ec/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fde3588c0d9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fde365b6168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fde359ac050 RCX: 00007fde3588c0d9 RDX: 000000000000ffdc RSI: 00000000200000c0 RDI: 000000000000000a RBP: 00007fde358e7ae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fde35acfb1f R14: 00007fde365b6300 R15: 0000000000022000 </TASK> Allocated by task 7618: kasan_save_stack+0x22/0x40 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x82/0x90 mm/kasan/common.c:325 kasan_slab_alloc include/linux/kasan.h:201 [inline] slab_post_alloc_hook mm/slab.h:737 [inline] slab_alloc_node mm/slub.c:3398 [inline] slab_alloc mm/slub.c:3406 [inline] __kmem_cache_alloc_lru mm/slub.c:3413 [inline] kmem_cache_alloc+0x2b4/0x3d0 mm/slub.c:3422 dst_alloc+0x14a/0x1f0 net/core/dst.c:92 ip6_dst_alloc+0x32/0xa0 net/ipv6/route.c:344 ip6_rt_pcpu_alloc net/ipv6/route.c:1369 [inline] rt6_make_pcpu_route net/ipv6/route.c:1417 [inline] ip6_pol_route+0x901/0x1190 net/ipv6/route.c:2254 pol_lookup_func include/net/ip6_fib.h:582 [inline] fib6_rule_lookup+0x52e/0x6f0 net/ipv6/fib6_rules.c:121 ip6_route_output_flags_noref+0x2e6/0x380 net/ipv6/route.c:2625 ip6_route_output_flags+0x76/0x320 net/ipv6/route.c:2638 ip6_route_output include/net/ip6_route.h:98 [inline] ip6_dst_lookup_tail+0x5ab/0x1620 net/ipv6/ip6_output.c:1092 ip6_dst_lookup_flow+0x90/0x1d0 net/ipv6/ip6_output.c:1222 ip6_sk_dst_lookup_flow+0x553/0x980 net/ipv6/ip6_output.c:1260 udpv6_sendmsg+0x151d/0x2c80 net/ipv6/udp.c:1554 inet6_sendmsg+0x9d/0xe0 net/ipv6/af_inet6.c:665 sock_sendmsg_nosec n ---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.
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/6b6d3be3661bff2746cab26147bd629aa034e094
- git.kernel.org/stable/c/7390c70bd431cbfa6951477e2c80a301643e284b
- git.kernel.org/stable/c/7e0dcd5f3ade221a6126278aca60c8ab4cc3bce9
- git.kernel.org/stable/c/803e84867de59a1e5d126666d25eb4860cfd2ebe
- git.kernel.org/stable/c/8208d7e56b1e579320b9ff3712739ad2e63e1f86
- git.kernel.org/stable/c/9b1a468a455d8319041528778d0e684a4c062792
- git.kernel.org/stable/c/b3d7ff8c04a83279fb7641fc4d5aa82a602df7c0
Recent Use After Free vulnerabilities
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- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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