Out-of-bounds Write Affecting kernel-rt-doc package, versions *


Severity

Recommended
0.0
high
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.14% (5th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-RHEL7-KERNELRTDOC-18190966
  • 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 RHEL:7 kernel-rt-doc.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-doc package and not the kernel-rt-doc package as distributed by RHEL. See How to fix? for RHEL:7 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