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CVE-2026-89554— mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction

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.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于mptcp_token_join_cookie_init_state函数在重建MP_JOIN请求套接字时未恢复local_id字段，导致subflow_ulp_clone读取到未初始化值，攻击者可通过发送并发MP_JOIN SYN影响该值，破坏路径管理器的子流记账。

CVSS 8.2 · High EPSS 0.60% · P47

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 4534e0eead692bb069ad1e6a5a245fc2e2078300 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 63cacb05e51a1c6e1349d2e593d00fd6ef43def4 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 954b5ea836eb118d188975ced803448537ab8479 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 9df36a4846375a9b75bf42d77bfed216b0f366f9 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 64f2c5dd49b956a542c8c02b8dad5d262a462bba affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< 51887ccd88791ddaa8755a7c614fda031ecf7982 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< bf19d166337c6488b39cb03eeeffb30a941d6326 affected
9466a1ccebbe54ac57fb8a89c2b4b854826546a8< b878dfdd12d7a5b8722a78d35e313506140ca3d9 affected
… +10 more rows
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I. Basic Information for CVE-2026-89554

Vulnerability Information
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Vulnerability Title
mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce, backup, join_id, token and msk from the saved cookie entry when rebuilding the request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it does not restore local_id, even though the SYN path saved it. subflow_ulp_clone() then reads that uninitialized field and stores it as the joined subflow's address-ID. Because the request-sock slab is SLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale byte of a previously freed request socket, which an off-path peer can influence by sending concurrent MP_JOIN SYNs. This corrupts the path manager's id-based subflow bookkeeping for the connection. Restore subflow_req->local_id from the cookie entry, as done for the other fields.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于mptcp_token_join_cookie_init_state函数在重建MP_JOIN请求套接字时未恢复local_id字段，导致subflow_ulp_clone读取到未初始化值，攻击者可通过发送并发MP_JOIN SYN影响该值，破坏路径管理器的子流记账。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 ~ 4534e0eead692bb069ad1e6a5a245fc2e2078300 -
Linux Linux 5.9 -

II. Public POCs for CVE-2026-89554

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III. Intelligence Information for CVE-2026-89554

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Patches & Fixes for CVE-2026-89554 (8)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89656 9.8 CRITICAL libceph: reject buckets with mismatched CRUSH ids
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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