Out-of-bounds Write Affecting kernel-devel package, versions *


Severity

Recommended
0.0
high
0
10

Based on CentOS security rating.

Threat Intelligence

EPSS
0.14% (5th percentile)

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  • Snyk IDSNYK-CENTOS6-KERNELDEVEL-18196699
  • published22 Jul 2026
  • disclosed19 Jul 2026

Introduced: 19 Jul 2026

NewCVE-2026-64009  (opens in a new tab)
CWE-787  (opens in a new tab)

How to fix?

There is no fixed version for Centos:6 kernel-devel.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-devel package and not the kernel-devel package as distributed by Centos. See How to fix? for Centos:6 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

xfrm: Check for underflow in xfrm_state_mtu

Leo Lin reported OOB write issue in esp component:

xfrm_state_mtu() returns u32 but performs its arithmetic in unsigned modulo-2^32 space using an attacker-influenced "header_len + authsize + net_adj" subtracted from a small "mtu" argument. A nobody user can install an IPv4 ESP tunnel SA with a large authentication key (XFRMA_ALG_AUTH_TRUNC, e.g. hmac(sha512), 64-byte key, 64-byte trunc), configure a small interface MTU (68 bytes), and set XFRMA_TFCPAD to a large value. When a single UDP datagram is then sent through the tunnel, xfrm_state_mtu() underflows to a near-2^32 value, and esp_output() consumes it as a signed int via:

    padto      = min(x->tfcpad, xfrm_state_mtu(x, mtu_cached))
    esp.tfclen = padto - skb->len   (assigned to int)

esp.tfclen ends up negative (e.g. -207). It is sign-extended to size_t when passed to memset() inside esp_output_fill_trailer(), producing a ~16 EB write of zeroes at skb_tail_pointer(skb). KASAN logs it as "Write of size 18446744073709551537 at addr ffff888...".

Check for underflow and return 1. This causes the sendmsg attempt to fail with ENETUNREACH.

CVSS Base Scores

version 3.1