Use After Free Affecting kernel package, versions <0:4.14.350-266.564.amzn2


Severity

Recommended
medium

Based on Amazon Linux security rating.

Threat Intelligence

Exploit Maturity
Mature
EPSS
0.11% (45th percentile)

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  • Snyk IDSNYK-AMZN2-KERNEL-7725124
  • published21 Aug 2024
  • disclosed10 Jun 2024

Introduced: 10 Jun 2024

CVE-2024-36971  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2 kernel to version 0:4.14.350-266.564.amzn2 or higher.
This issue was patched in ALAS2-2024-2622.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel package and not the kernel package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2 relevant fixed versions and status.

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

net: fix __dst_negative_advice() race

__dst_negative_advice() does not enforce proper RCU rules when sk->dst_cache must be cleared, leading to possible UAF.

RCU rules are that we must first clear sk->sk_dst_cache, then call dst_release(old_dst).

Note that sk_dst_reset(sk) is implementing this protocol correctly, while __dst_negative_advice() uses the wrong order.

Given that ip6_negative_advice() has special logic against RTF_CACHE, this means each of the three ->negative_advice() existing methods must perform the sk_dst_reset() themselves.

Note the check against NULL dst is centralized in __dst_negative_advice(), there is no need to duplicate it in various callbacks.

Many thanks to Clement Lecigne for tracking this issue.

This old bug became visible after the blamed commit, using UDP sockets.

CVSS Scores

version 3.1