Linux: Use After Free
CVE-2026-23273 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 91e4ff8d966978901630fc29582c1a76d3c6e46c, 3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4, 721eb342d9ba19bad5c4815ea3921465158b7362 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 0.14% 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 91e4ff8d966978901630fc29582c1a76d3c6e46c or 3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4 or 721eb342d9ba19bad5c4815ea3921465158b7362 or 19c7d8ac51988d053709c1e85bd8482076af845d, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.252 or 5.15.202 or 6.1.165 or 6.6.128, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | da5c6b8ae47e414be47e5e04def15b25d5c962dc up to, but not including, 91e4ff8d966978901630fc29582c1a76d3c6e46c; 5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a up to, but not including, 3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4; c43d0e787cbba569ec9d11579ed370b50fab6c9c up to, but not including, 721eb342d9ba19bad5c4815ea3921465158b7362; 11ba9f0dc865136174cb98834280fb21bbc950c7 up to, but not including, 19c7d8ac51988d053709c1e85bd8482076af845d; 986967a162142710076782d5b93daab93a892980 up to, but not including, a1f686d273d129b45712d95f4095843b864466bd; cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66 up to, but not including, d34f7a8aa9a25b7e64e0e46e444697c0f702374d; f8db6475a83649689c087a8f52486fcc53e627e9 up to, but not including, 1e58ae87ad1e6e24368dea9aec9048c758cd0e2b; f8db6475a83649689c087a8f52486fcc53e627e9 up to, but not including, e3f000f0dee1bfab52e2e61ca6a3835d9e187e35; and 7 more ranges | 91e4ff8d966978901630fc29582c1a76d3c6e46c, 3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4, 721eb342d9ba19bad5c4815ea3921465158b7362, 19c7d8ac51988d053709c1e85bd8482076af845d, a1f686d273d129b45712d95f4095843b864466bd, d34f7a8aa9a25b7e64e0e46e444697c0f702374d |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 5.10.250 up to, but not including, 5.10.252; 5.15.200 up to, but not including, 5.15.202; 6.1.163 up to, but not including, 6.1.165; 6.6.124 up to, but not including, 6.6.128; 6.12.70 up to, but not including, 6.12.75; 6.18.10 up to, but not including, 6.18.14; 6.19.1 up to, but not including, 6.19.4 | 5.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.14 |
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 CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: macvlan: observe an RCU grace period in macvlan_common_newlink() error path valis reported that a race condition still happens after my prior patch. macvlan_common_newlink() might have made @dev visible before detecting an error, and its caller will directly call free_netdev(dev). We must respect an RCU period, either in macvlan or the core networking stack. After adding a temporary mdelay(1000) in macvlan_forward_source_one() to open the race window, valis repro was: ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2 ip link add mv0 link p2 type macvlan mode source (ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20 &) ; sleep 0.5 ; ping -c1 -I p1 1.2.3.4 PING 1.2.3.4 (1.2.3.4): 56 data bytes RTNETLINK answers: Invalid argument BUG: KASAN: slab-use-after-free in macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) Read of size 8 at addr ffff888016bb89c0 by task e/175 CPU: 1 UID: 1000 PID: 175 Comm: e Not tainted 6.19.0-rc8+ #33 NONE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:123) print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) ? macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) kasan_report (mm/kasan/report.c:597) ? macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) ? tasklet_init (kernel/softirq.c:983) macvlan_handle_frame (drivers/net/macvlan.c:501) Allocated by task 169: kasan_save_stack (mm/kasan/common.c:58) kasan_save_track (./arch/x86/include/asm/current.h:25 mm/kasan/common.c:70 mm/kasan/common.c:79) __kasan_kmalloc (mm/kasan/common.c:419) __kvmalloc_node_noprof (./include/linux/kasan.h:263 mm/slub.c:5657 mm/slub.c:7140) alloc_netdev_mqs (net/core/dev.c:12012) rtnl_create_link (net/core/rtnetlink.c:3648) rtnl_newlink (net/core/rtnetlink.c:3830 net/core/rtnetlink.c:3957 net/core/rtnetlink.c:4072) rtnetlink_rcv_msg (net/core/rtnetlink.c:6958) netlink_rcv_skb (net/netlink/af_netlink.c:2550) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:727 net/socket.c:742 net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:131) Freed by task 169: kasan_save_stack (mm/kasan/common.c:58) kasan_save_track (./arch/x86/include/asm/current.h:25 mm/kasan/common.c:70 mm/kasan/common.c:79) kasan_save_free_info (mm/kasan/generic.c:587) __kasan_slab_free (mm/kasan/common.c:287) kfree (mm/slub.c:6674 mm/slub.c:6882) rtnl_newlink (net/core/rtnetlink.c:3845 net/core/rtnetlink.c:3957 net/core/rtnetlink.c:4072) rtnetlink_rcv_msg (net/core/rtnetlink.c:6958) netlink_rcv_skb (net/netlink/af_netlink.c:2550) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:727 net/socket.c:742 net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:131)
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: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/19c7d8ac51988d053709c1e85bd8482076af845d
- git.kernel.org/stable/c/1e58ae87ad1e6e24368dea9aec9048c758cd0e2b
- git.kernel.org/stable/c/3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4
- git.kernel.org/stable/c/721eb342d9ba19bad5c4815ea3921465158b7362
- git.kernel.org/stable/c/91e4ff8d966978901630fc29582c1a76d3c6e46c
- git.kernel.org/stable/c/a1f686d273d129b45712d95f4095843b864466bd
- git.kernel.org/stable/c/d34f7a8aa9a25b7e64e0e46e444697c0f702374d
- git.kernel.org/stable/c/e3f000f0dee1bfab52e2e61ca6a3835d9e187e35
Other references
Recent Use After Free vulnerabilities
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- 8.8 High severity
- 8.8 High severity
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