CVE-2026-64422: Linux kernel · Integer Overflow
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 7.1 High · fixed in f0d88a4cd03affff6c08adf6c63964e235aede43 : patch Linux kernel soon.
Data as of 26 Oct 2026, 17:30 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in f0d88a4cd03affff6c08adf6c63964e235aede43, efb8763d7bbb40cff4cc55a6b62c3095a038149c, e81f805824a8109504fce090641b17d135b48cd1 +5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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.
References
- git.kernel.org/stable/c/f0d88a4cd03affff6c08adf6c63964e235aede43 (opens in a new tab)
- git.kernel.org/stable/c/27ddf4486c7dbf5bdd393fa8bef6b67179796d98 (opens in a new tab)
- git.kernel.org/stable/c/782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae (opens in a new tab)
- git.kernel.org/stable/c/e81f805824a8109504fce090641b17d135b48cd1 (opens in a new tab)
- git.kernel.org/stable/c/99206ce2244f8a3ed64298d0667c9055845a5dc7 (opens in a new tab)
- git.kernel.org/stable/c/bbae351c0f32f7c200249e4aa6561b2b419dcf69 (opens in a new tab)
- git.kernel.org/stable/c/a094ac95d3b69adfa1676eb9c8eae6835d4f1671 (opens in a new tab)
- git.kernel.org/stable/c/efb8763d7bbb40cff4cc55a6b62c3095a038149c (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)