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CVE-2026-89554

mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 4534e0eead692bb069ad1e6a5a245fc2e2078300; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 63cacb05e51a1c6e1349d2e593d00fd6ef43def4; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 954b5ea836eb118d188975ced803448537ab8479; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 9df36a4846375a9b75bf42d77bfed216b0f366f9; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 64f2c5dd49b956a542c8c02b8dad5d262a462bba; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in 51887ccd88791ddaa8755a7c614fda031ecf7982; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in bf19d166337c6488b39cb03eeeffb30a941d6326; From 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 · fixed in b878dfdd12d7a5b8722a78d35e313506140ca3d9

  • Linux Linux

    5.9

  • KernelLinux

    From 5.9.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org