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  4. CVE 2026 64422 net ipv4 bound tcp reordering sysctl writes and
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High ยท CVSS 7.1CVE-2026-64422

net: ipv4: bound TCP reordering sysctl writes and MTU probe sizesCVE-2026-64422

Answer in brief

CVE-2026-64422 records a High severity (CVSS 7.1) vulnerability in net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 25, 2026Updated Oct 19, 2026Source checked Nov 6, 2026First seen by HOL Aug 5, 2026Material review Oct 19, 2026
Upstream Advisory

Key facts

Risk
High ยท CVSS 7.1
Exploitation
Not marked as known exploited
Affected software
15 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 7.1. 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.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Affected products and reported versions
ProductAffected versionsFixed versions
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:-:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:rc4:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:rc5:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:rc6:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:rc7:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:2.6.24:rc8:*:*:*:*:*:*Not reportedNot reported
Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Linux/Linuxgeneric>=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <f0d88a4cd03affff6c08adf6c63964e235aede43 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <27ddf4486c7dbf5bdd393fa8bef6b67179796d98 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <e81f805824a8109504fce090641b17d135b48cd1 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <99206ce2244f8a3ed64298d0667c9055845a5dc7 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <bbae351c0f32f7c200249e4aa6561b2b419dcf69 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <a094ac95d3b69adfa1676eb9c8eae6835d4f1671 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <efb8763d7bbb40cff4cc55a6b62c3095a038149cf0d88a4cd03affff6c08adf6c63964e235aede43, 27ddf4486c7dbf5bdd393fa8bef6b67179796d98, 782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae, e81f805824a8109504fce090641b17d135b48cd1, 99206ce2244f8a3ed64298d0667c9055845a5dc7, bbae351c0f32f7c200249e4aa6561b2b419dcf69, a094ac95d3b69adfa1676eb9c8eae6835d4f1671, efb8763d7bbb40cff4cc55a6b62c3095a038149c
Linux/Linuxgeneric2.6.24Not reported
Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.7 <**
Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric>=V3.1.7 <**
Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.7 <**

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux, Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP.
  2. 2Review the reported fix. Update Linux/Linux to f0d88a4cd03affff6c08adf6c63964e235aede43; Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to *; Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP to * if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Jul 25, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 19, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Aug 5, 2026

Sources and claim methodology

  • Source referencecert-portal.siemens.com
  • Source referencecert-portal.siemens.com
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
Upstream source description

In the Linux kernel, the following vulnerability has been resolved: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP socket state. The sysctl is stored as an `int` but copied into the `u32` `tp->reordering` field for new sockets, so negative writes wrap to large values. With `tcp_mtu_probing=2`, the wrapped value can overflow the `tcp_mtu_probe()` size calculation and drive the MTU probing path into an out-of-bounds read. Route `tcp_reordering` writes through `proc_dointvec_minmax()` and require it to be at least 1. Also require `tcp_max_reordering` to be at least 1 so the configured maximum cannot become negative either. When registering the table for a non-init network namespace, relocate `extra2` pointers that refer into `init_net.ipv4` so the `tcp_reordering` upper bound follows that namespace's `tcp_max_reordering`. Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`. This keeps the send queue and window checks from being bypassed through signed integer overflow.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-190
Source
CVE List V5
Source checked
Nov 6, 2026
References
10 linked sources
Open source record