Answer in brief
CVE-2026-89554 records a High severity (CVSS 8.2) vulnerability in mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <64f2c5dd49b956a542c8c02b8dad5d262a462bba || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <51887ccd88791ddaa8755a7c614fda031ecf7982 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <bf19d166337c6488b39cb03eeeffb30a941d6326 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <b878dfdd12d7a5b8722a78d35e313506140ca3d9 | 64f2c5dd49b956a542c8c02b8dad5d262a462bba, 51887ccd88791ddaa8755a7c614fda031ecf7982, bf19d166337c6488b39cb03eeeffb30a941d6326, b878dfdd12d7a5b8722a78d35e313506140ca3d9 |
| Linux/Linuxgeneric | 5.9 | Not reported |
| Linux/Linuxgeneric | >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <4534e0eead692bb069ad1e6a5a245fc2e2078300 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <63cacb05e51a1c6e1349d2e593d00fd6ef43def4 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <954b5ea836eb118d188975ced803448537ab8479 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <9df36a4846375a9b75bf42d77bfed216b0f366f9 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <64f2c5dd49b956a542c8c02b8dad5d262a462bba || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <51887ccd88791ddaa8755a7c614fda031ecf7982 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <bf19d166337c6488b39cb03eeeffb30a941d6326 || >=9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <b878dfdd12d7a5b8722a78d35e313506140ca3d9 | 4534e0eead692bb069ad1e6a5a245fc2e2078300, 63cacb05e51a1c6e1349d2e593d00fd6ef43def4, 954b5ea836eb118d188975ced803448537ab8479, 9df36a4846375a9b75bf42d77bfed216b0f366f9, 64f2c5dd49b956a542c8c02b8dad5d262a462bba, 51887ccd88791ddaa8755a7c614fda031ecf7982, bf19d166337c6488b39cb03eeeffb30a941d6326, b878dfdd12d7a5b8722a78d35e313506140ca3d9 |
Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 11, 2026
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.
Quoted source text, attributed separately from HOL analysis.