NULL Pointer Dereference Affecting kernel-64k-debug package, versions <0:5.14.0-362.8.1.el9_3


Severity

Recommended
high

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.04% (12th percentile)

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  • Snyk IDSNYK-RHEL9-KERNEL64KDEBUG-8461618
  • published5 Dec 2024
  • disclosed24 May 2024

Introduced: 24 May 2024

CVE-2021-47515  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

Upgrade RHEL:9 kernel-64k-debug to version 0:5.14.0-362.8.1.el9_3 or higher.
This issue was patched in RHSA-2023:6583.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-64k-debug package and not the kernel-64k-debug package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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

seg6: fix the iif in the IPv6 socket control block

When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510):

IPCB(skb)-&gt;iif = skb-&gt;skb_iif;

If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation. In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):

memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

The memset(...) was introduced in commit ef489749aae5 ("ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation") a long time ago (2019-01-29).

Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero).

As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 ("ipv6: When forwarding count rx stats on the orig netdev") is applied.

To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.

CVSS Scores

version 3.1