Status: UPDATED | Advisory ID: CVE-2026-31669
| CVE | CVE-2026-31669 |
| CVSS Score / Version | 9.8 (Critical) / CVSS v3.1 |
| Updated | 2026-07-14 |
| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CVSS Prose | attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is high; integrity impact is high; availability impact is high. |
| Affected products | Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, and Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
| Classified as | CWE-416 (Use After Free) |
| Vendor | Product | Affected Versions | Patch Status |
|---|---|---|---|
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP | ||
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP | ||
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
| Subsystems | General OT |
| Sectors | Multiple |
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. (NVD)
Monitor Siemens's web page for any future patch releases.
| Source | Reference |
|---|---|
| NVD | https://nvd.nist.gov/vuln/detail/CVE-2026-31669 |
| CVE | https://www.cve.org/CVERecord?id=CVE-2026-31669 |