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| Vulnerability ID | VCID-ht2j-bafp-eudq |
| Aliases |
CVE-2026-31669
|
| Summary | In the Linux kernel, the following vulnerability has been resolved: mptcp: fix slab-use-after-free in __inet_lookup_established The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register(). However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established. Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 6.6 |
| Risk | 3.3 |
| Affected and Fixed Packages | Package Details |
| System | Score | Found at |
|---|---|---|
| cvssv3 | 7.0 | https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-31669.json |
| cvssv3 | 7.3 | https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-31669.json |
| epss | 0.0003 | https://api.first.org/data/v1/epss?cve=CVE-2026-31669 |
| epss | 0.00068 | https://api.first.org/data/v1/epss?cve=CVE-2026-31669 |
| cvssv3.1 | 7 | https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Percentile | 0.08624 |
| EPSS Score | 0.0003 |
| Published At | April 26, 2026, 12:55 p.m. |
| Date | Actor | Action | Source | VulnerableCode Version |
|---|---|---|---|---|
| 2026-04-25T23:21:43.222230+00:00 | Debian Importer | Import | https://security-tracker.debian.org/tracker/data/json | 38.4.0 |