---
id: CVE-2026-90110
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  inetpeer: randomize RB-tree node comparison using SipHash

  The inetpeer rate limiting system stores peer entries in a Red-Black tree
  keyed deterministically on the remo…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  inetpeer: randomize RB-tree node comparison using SipHash

  The inetpeer rate limiting system stores peer entries in a Red-Black tree
  keyed deterministically on the remo…
severity: critical
cvss: 9.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    b20e98f0bb668a59abaf7bcf85d75c073e90d352
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    5f127e3cc9647a8a70db12c65dbd0de473545380
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    199fcf285e498111e029137d088949bc6c26d578
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    857681f6835d5b0a7bc4a34a026baeaaf5215623
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    7109bb63667a53e4542ad845476f97d0c8b28a61
  - >-
    Linux >= b145425f269a17ed344d737f746b844dfac60c82 <
    2ee66e9487172fcd189bc52a767c30dad7141c09
  - Linux 4.14
published: '2026-09-17'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T18:17:42.327'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90110'
references:
  - url: 'https://git.kernel.org/stable/c/199fcf285e498111e029137d088949bc6c26d578'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2ee66e9487172fcd189bc52a767c30dad7141c09'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5f127e3cc9647a8a70db12c65dbd0de473545380'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7109bb63667a53e4542ad845476f97d0c8b28a61'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/857681f6835d5b0a7bc4a34a026baeaaf5215623'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b20e98f0bb668a59abaf7bcf85d75c073e90d352'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00638
epssPercentile: 0.48302
ingestedAt: '2026-09-17T16:21:47.887Z'
---

## Overview

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

inetpeer: randomize RB-tree node comparison using SipHash

The inetpeer rate limiting system stores peer entries in a Red-Black tree
keyed deterministically on the remote IP address. Because tree lookups walk
the RB-tree using standard lexicographical comparisons (inetpeer_addr_cmp),
an off-path adversary can predict the exact topology of the tree and the
sequence of nodes traversed during lookups (the gc_stack candidate list).

By combining deterministic tree traversal with aggressive garbage collection
(triggered when tree size exceeds inet_peer_threshold), an attacker can
selectively force the eviction of targeted inet_peer nodes. When an evicted
node is subsequently re-created upon receiving a new packet, its rate-limiting
token bucket (rate_tokens, rate_last) is reset to full capacity. This creates
a side-channel primitive allowing off-path attackers to bypass IP-keyed ICMP
rate limits and infer open UDP ports (similar to SAD DNS style attacks).

Mitigate this by randomizing the RB-tree node comparison logic using SipHash
with a secret key (inetpeer_hash_key) initialized via net_get_random_once().
Nodes are ordered in the tree by SipHash(addr, key) rather than raw IP
addresses. Because the secret key is unknown to external entities, the tree
layout and lookup traversal paths are unpredictable to off-path adversaries,
breaking the deterministic eviction gadget.

Cache the computed 64-bit SipHash (hash) in struct inet_peer and compute the
target hash (dhash) once at the beginning of inet_getpeer() to avoid recomputing
SipHash at every step of the RB-tree walk.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.