CVE-2021-47515

Medium

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)->iif = skb->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.

Package Linux Kernel
Published 2024-05-24
Last modified 2025-09-24
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-476

CVE-2021-47515 is a NULL Pointer Dereference vulnerability

What is NULL Pointer Dereference?

The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. Learn more on MITRE CWE

Affected versions

Linux kernel versions 4.14.98, 4.19.20, 4.20.7, 5.0 and later are affected. Fixed in 4.14.258, 4.19.221, 5.4.165, 5.10.85, 5.15.8, 5.16 and their respective stable series.

Affected from
≥ 4.14.98 ≥ 4.19.20 ≥ 4.20.7 ≥ 5.0
Fixed in
✓ 4.14.258 4.14.x ✓ 4.19.221 4.19.x ✓ 5.4.165 5.4.x ✓ 5.10.85 5.10.x ✓ 5.15.8 5.15.x ✓ 5.16

References

6 total
Showing 5 of 6 references View all on NVD

Frequently asked questions

  • What is CVE-2021-47515?

    CVE-2021-47515 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as a NULL Pointer Dereference flaw (CWE-476) . It affects Linux kernel versions from 4.14.98 onward and has been patched in 4.14.258, 4.19.221, 5.4.165 and others. CVE-2021-47515 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2021-47515?

    CVE-2021-47515 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2021-47515?

    Yes. CVE-2021-47515 has been patched. Fixed versions include 4.14.258, 4.19.221, 5.4.165 and others. If you are running Linux kernel 4.14.98 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2021-47515 actively exploited?

    No. CVE-2021-47515 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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