ipv4: free inet_opt and ireq_opt after an RCU grace period

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98432
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-15 13:17:13 UTC
Updated2026-10-31 21:16:53 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.004570000 probability, percentile 0.396730000 (date 2026-10-31)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 b3b027ef0cd322bfa839b9aaf5b27551eea54cf6 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 95a8c8fa9f27dce64c40c41c062de7728bf34ab5 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 89b5b1eb7d633c33832b7ff2c02e19a144705036 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 742f73df544e03744f2981c467d6542fe8172a2a git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 11a03ce3c4a62d84c10ccdfe47f8075006498568 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 a47406c769f72c070386985488f1c4d057df86b2 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 26d4c36d318cffbbd160884a0e4cec0da4da4936 git Not specified
CNA Linux Linux affected 079096f103faca2dd87342cca6f23d4b34da8871 e3f33b0a1d89d738e2b913dab519226eaf76e15b git Not specified
CNA Linux Linux affected 4.4 Not specified
CNA Linux Linux unaffected 4.4 semver Not specified
CNA Linux Linux unaffected 5.10.272 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.223 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.190 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.159 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.56 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.10 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/95a8c8fa9f27dce64c40c41c062de7728bf34ab5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/89b5b1eb7d633c33832b7ff2c02e19a144705036 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
www.openwall.com/lists/oss-security/2026/10/31/5 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
git.kernel.org/stable/c/11a03ce3c4a62d84c10ccdfe47f8075006498568 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/26d4c36d318cffbbd160884a0e4cec0da4da4936 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
www.openwall.com/lists/oss-security/2026/10/30/6 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
www.openwall.com/lists/oss-security/2026/10/30/1 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
git.kernel.org/stable/c/b3b027ef0cd322bfa839b9aaf5b27551eea54cf6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e3f33b0a1d89d738e2b913dab519226eaf76e15b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a47406c769f72c070386985488f1c4d057df86b2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/742f73df544e03744f2981c467d6542fe8172a2a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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