Linux: Use After Free
CVE-2026-98432 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions b3b027ef0cd322bfa839b9aaf5b27551eea54cf6, 95a8c8fa9f27dce64c40c41c062de7728bf34ab5, 89b5b1eb7d633c33832b7ff2c02e19a144705036 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 0.78% chance of exploitation within 30 days, higher than 56% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to b3b027ef0cd322bfa839b9aaf5b27551eea54cf6 or 95a8c8fa9f27dce64c40c41c062de7728bf34ab5 or 89b5b1eb7d633c33832b7ff2c02e19a144705036 or 742f73df544e03744f2981c467d6542fe8172a2a, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.272 or 5.15.223 or 6.1.190 or 6.6.159, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, b3b027ef0cd322bfa839b9aaf5b27551eea54cf6; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, 95a8c8fa9f27dce64c40c41c062de7728bf34ab5; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, 89b5b1eb7d633c33832b7ff2c02e19a144705036; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, 742f73df544e03744f2981c467d6542fe8172a2a; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, 11a03ce3c4a62d84c10ccdfe47f8075006498568; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, a47406c769f72c070386985488f1c4d057df86b2; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, 26d4c36d318cffbbd160884a0e4cec0da4da4936; 079096f103faca2dd87342cca6f23d4b34da8871 up to, but not including, e3f33b0a1d89d738e2b913dab519226eaf76e15b; and 1 more ranges | b3b027ef0cd322bfa839b9aaf5b27551eea54cf6, 95a8c8fa9f27dce64c40c41c062de7728bf34ab5, 89b5b1eb7d633c33832b7ff2c02e19a144705036, 742f73df544e03744f2981c467d6542fe8172a2a, 11a03ce3c4a62d84c10ccdfe47f8075006498568, a47406c769f72c070386985488f1c4d057df86b2 |
| Linux | Linux Kernel | 4.4 up to, but not including, 5.10.272; 5.11 up to, but not including, 5.15.223; 5.16 up to, but not including, 6.1.190; 6.2 up to, but not including, 6.6.159; 6.7 up to, but not including, 6.12.113; 6.13 up to, but not including, 6.18.56; 6.19 up to, but not including, 7.2.10; 7.3 | 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/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: ipv4: free inet_opt and ireq_opt after an RCU grace period tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another cpu can concurrently process a retransmitted SYN for the same request socket, and send a SYNACK from tcp_check_req(). tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice. Note that the SYNACK timer itself is not an issue: it holds a reference on its request socket, and inet_csk_reqsk_queue_drop() calls timer_delete_sync() before the child can be freed. Since commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table"), request sockets are processed without holding the listener lock, so nothing prevents the child socket from being freed while the SYNACK is still being built. TCP child sockets do not have SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree(), leading to a use-after-free in ip_options_build(). A similar issue exists with request socket migration (net.ipv4.tcp_migrate_req=1, or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program). reqsk_timer_handler() clones the request socket with inet_reqsk_clone(), so that the old request socket and its clone share the same ireq_opt, then reqsk_migrate_reset() clears the pointer in the old one. Another cpu holding a reference on the old request socket can still be using these options (sending a SYNACK, or creating a child in tcp_v4_syn_recv_sock()) when the clone is freed, and tcp_v4_reqsk_destructor() also uses a plain kfree(). Readers already use RCU, and other paths replacing inet_opt (do_ip_setsockopt(), cipso_v4_sock_setattr()...) already use kfree_rcu(). Use kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor() as well. IPv6 is not affected by the first issue, because tcp_v6_syn_recv_sock() duplicates the options. tcp_v6_reqsk_destructor() has the same migration issue with ipv6_opt, which is only set by CALIPSO. This will be addressed in a separate patch.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/11a03ce3c4a62d84c10ccdfe47f8075006498568
- git.kernel.org/stable/c/26d4c36d318cffbbd160884a0e4cec0da4da4936
- git.kernel.org/stable/c/742f73df544e03744f2981c467d6542fe8172a2a
- git.kernel.org/stable/c/89b5b1eb7d633c33832b7ff2c02e19a144705036
- git.kernel.org/stable/c/95a8c8fa9f27dce64c40c41c062de7728bf34ab5
- git.kernel.org/stable/c/a47406c769f72c070386985488f1c4d057df86b2
- git.kernel.org/stable/c/b3b027ef0cd322bfa839b9aaf5b27551eea54cf6
- git.kernel.org/stable/c/e3f33b0a1d89d738e2b913dab519226eaf76e15b
Third-party and government advisories
- openwall.com/lists/oss-security/2026/10/30/1Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2026/10/30/6Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2026/10/31/5Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2026/11/03/1Mailing List, Third Party Advisory
Recent Use After Free vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.1 High severity
- 7.2 High severity
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