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TI-2021-22165 Aliases CVE-2021-47515

seg6: fix the iif in the IPv6 socket control block

Priority LOW 34CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-476.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00746 55th percentileScored 2026-11-07
Fix Partial Linux (Linux): 4.14.258, 4.19.221, 4.21 +4Red Hat: 1 advisoryRed Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux4.14.98 to before 4.14.258; 4.19.20 to before 4.19.221; 4.20.7 to before 4.214.14.258, 4.19.221, 4.21Patch availableCNA
LinuxLinux5.0 and later4.14.258, 4.19.221, 5.4.165, 5.10.85, 5.15.8, 5.16Patch availableCNA
  • Linux VendorLinux Affected 4.14.98 to before 4.14.258; 4.19.20 to before 4.19.221; 4.20.7 to before 4.21 Fixed in 4.14.258, 4.19.221, 4.21 Patch available CNA
  • Linux VendorLinux Affected 5.0 and later Fixed in 4.14.258, 4.19.221, 5.4.165, 5.10.85, 5.15.8, 5.16 Patch available CNA

CPE configurations NVD · 9

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*4.14.98 to before 4.14.258; 4.19.20 to before 4.19.221; 4.20.7 to before 5.0; 5.0.1 to before 5.4.165; 5.5 to before 5.10.85; 5.11 to before 5.15.8VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.0:-:*:*:*:*:*:*5.0VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.0:rc6:*:*:*:*:*:*5.0 rc6VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.0:rc7:*:*:*:*:*:*5.0 rc7VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.0:rc8:*:*:*:*:*:*5.0 rc8VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*5.16 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*5.16 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:*5.16 rc3VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:*5.16 rc4VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.14.98 to before 4.14.258; 4.19.20 to before 4.19.221; 4.20.7 to before 5.0; 5.0.1 to before 5.4.165; 5.5 to before 5.10.85; 5.11 to before 5.15.8 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.0:-:*:*:*:*:*:* Versions 5.0 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.0:rc6:*:*:*:*:*:* Versions 5.0 rc6 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.0:rc7:*:*:*:*:*:* Versions 5.0 rc7 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.0:rc8:*:*:*:*:*:* Versions 5.0 rc8 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:* Versions 5.16 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* Versions 5.16 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* Versions 5.16 rc3 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:* Versions 5.16 rc4 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 4.14.258, 4.19.221, 4.21
  • Fix · CNA Linux (Linux) Fixed in 4.14.258, 4.19.221, 5.4.165, 5.10.85, 5.15.8, 5.16

Red Hat 1 advisory

  • RHSA-2023:6583 Released 2023-11-07 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat CodeReady Linux Builder (v. 9) kernel-tools-libs-devel-5.14.0-362.8.1.el9_3, libperf-5.14.0-362.8.1.el9_3
    • Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-362.8.1.el9_3, kernel-64k-debug-devel-matched-5.14.0-362.8.1.el9_3, kernel-64k-devel-5.14.0-362.8.1.el9_3 +11
    • Red Hat Enterprise Linux BaseOS (v. 9) bpftool-7.2.0-362.8.1.el9_3, kernel-5.14.0-362.8.1.el9_3, kernel-64k-5.14.0-362.8.1.el9_3 +29
    • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-362.8.1.el9_3, kernel-rt-core-5.14.0-362.8.1.el9_3, kernel-rt-debug-5.14.0-362.8.1.el9_3 +9
    • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-362.8.1.el9_3, kernel-rt-core-5.14.0-362.8.1.el9_3, kernel-rt-debug-5.14.0-362.8.1.el9_3 +11

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 9AffectedNo fix planned: Will not fix
Not affected: 4 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47515

References

Patch 6

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences