mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction
Published Sep 11, 2026
8.2
HIGHCVSS 3.1
EPSS 0.60%
Description
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.
Affected products
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- Version StatusaffectedConstraints
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- Version 5.9StatusaffectedConstraints-
- Version 0StatusunaffectedConstraints<5.9
- Version 5.10.270StatusunaffectedConstraints<=5.10.*
- Version 5.15.221StatusunaffectedConstraints<=5.15.*
- Version 6.1.188StatusunaffectedConstraints<=6.1.*
- Version 6.12.109StatusunaffectedConstraints<=6.12.*
- Version 6.18.50StatusunaffectedConstraints<=6.18.*
- Version 6.6.157StatusunaffectedConstraints<=6.6.*
- Version 7.2.4StatusunaffectedConstraints<=7.2.*
- Version 7.3-rc1StatusunaffectedConstraints<=*
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||||||||
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| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data.
No data.
Red Hat Enterprise Linux 10
kernel
Fix deferred
Red Hat Enterprise Linux 10
kernel-rt
Fix deferred
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise Linux 8
kernel
Fix deferred
Red Hat Enterprise Linux 8
kernel-rt
Fix deferred
Red Hat Enterprise Linux 9
kernel
Fix deferred
Red Hat Enterprise Linux 9
kernel-rt
Fix deferred
Red Hat OpenShift Container Platform 4
openshift/ose-rhel-coreos-8
Fix deferred
Red Hat OpenShift Container Platform 4
openshift/ose-rhel-coreos-9
Fix deferred
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | n/a |
| Red Hat Enterprise Linux 10 | kernel-rt | Fix deferred | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel | Fix deferred | n/a |
| Red Hat Enterprise Linux 8 | kernel-rt | Fix deferred | n/a |
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | n/a |
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred | n/a |
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Fix deferred | n/a |
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Fix deferred | n/a |
No package ranges for this CVE.
Remediation
No remediation recorded yet.
References (13)
- https://access.redhat.com/security/cve/CVE-2026-89554 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2532504 Issue Tracking
- https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89554.mbox
- https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300
- https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982
- https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4
- https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba
- https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479
- https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9
- https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9
- https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326
- https://nvd.nist.gov/vuln/detail/CVE-2026-89554
- https://www.cve.org/CVERecord?id=CVE-2026-89554
Change history (0)
No recorded changes yet.