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 1518F-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.
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.
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 1518F-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:-:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:rc4:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:rc5:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:rc6:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:rc7:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:2.6.24:rc8:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <f0d88a4cd03affff6c08adf6c63964e235aede43 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <27ddf4486c7dbf5bdd393fa8bef6b67179796d98 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <e81f805824a8109504fce090641b17d135b48cd1 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <99206ce2244f8a3ed64298d0667c9055845a5dc7 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <bbae351c0f32f7c200249e4aa6561b2b419dcf69 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <a094ac95d3b69adfa1676eb9c8eae6835d4f1671 || >=91cc17c0e5e5ada156a8d5787a2509d263ea6bbf <efb8763d7bbb40cff4cc55a6b62c3095a038149c | f0d88a4cd03affff6c08adf6c63964e235aede43, 27ddf4486c7dbf5bdd393fa8bef6b67179796d98, 782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae, e81f805824a8109504fce090641b17d135b48cd1, 99206ce2244f8a3ed64298d0667c9055845a5dc7, bbae351c0f32f7c200249e4aa6561b2b419dcf69, a094ac95d3b69adfa1676eb9c8eae6835d4f1671, efb8763d7bbb40cff4cc55a6b62c3095a038149c |
| Linux/Linuxgeneric | 2.6.24 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.