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CVE-2026-98432— ipv4: free inet_opt and ireq_opt after an RCU grace period

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： IPv4：在 RCU 宽限期后释放 inet_opt 和 ireq_opt 在未进行拷贝的情况下，将 的所有权转移给了子套接字（ ）。 其他 CPU 可能会并发处理针对同一请求套接字的 SYN 重传，并通过 发送 SYN-ACK。 和 仅在 保护下读取 ，随后 和 会两次读取 。 注意，SYN-ACK 定时器本身并非问题所在：它持有对请求套接字的引用，并且在子套接字被释放之前， 会调用 。 自从提交 （“tcp/dccp: 将 syn_recv 请求安装到 ehash

AI Predicted 7.8 Difficulty: Hard EPSS 0.17% · P5

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 079096f103faca2dd87342cca6f23d4b34da8871< b3b027ef0cd322bfa839b9aaf5b27551eea54cf6 affected
079096f103faca2dd87342cca6f23d4b34da8871< 95a8c8fa9f27dce64c40c41c062de7728bf34ab5 affected
079096f103faca2dd87342cca6f23d4b34da8871< 89b5b1eb7d633c33832b7ff2c02e19a144705036 affected
079096f103faca2dd87342cca6f23d4b34da8871< 742f73df544e03744f2981c467d6542fe8172a2a affected
079096f103faca2dd87342cca6f23d4b34da8871< 11a03ce3c4a62d84c10ccdfe47f8075006498568 affected
079096f103faca2dd87342cca6f23d4b34da8871< a47406c769f72c070386985488f1c4d057df86b2 affected
079096f103faca2dd87342cca6f23d4b34da8871< 26d4c36d318cffbbd160884a0e4cec0da4da4936 affected
079096f103faca2dd87342cca6f23d4b34da8871< e3f33b0a1d89d738e2b913dab519226eaf76e15b affected
… +10 more rows
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I. Basic Information for CVE-2026-98432

Vulnerability Information
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Vulnerability Title
ipv4: free inet_opt and ireq_opt after an RCU grace period
Source: CVE Program / CVE List V5
Vulnerability 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: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 079096f103faca2dd87342cca6f23d4b34da8871 ~ b3b027ef0cd322bfa839b9aaf5b27551eea54cf6 -
Linux Linux 4.4 -

II. Public POCs for CVE-2026-98432

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III. Intelligence Information for CVE-2026-98432

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Other References for CVE-2026-98432 (8)

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-98432

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