Cloudanix VulnDB

CVE-2021-47014

None

CVSS

—

EPSS

0.2%

Published

Feb 28, 2024

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A bug in the Linux kernel's network handling can let specially crafted traffic crash the entire system.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Memory Corruption
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Overwriting the skb qdisc cb during fragment handling in act_ct can place attacker-controlled or random data into FRAG_CB(), causing subsequent wild memory accesses and crashes when inet_frag_rbtree_purge walks the rbtree.

Why it matters to the business

Kernel crashes or denial of service on systems performing connection tracking with IP fragmentation, leading to network service interruptions and potential loss of connectivity until reboot.

How an attack unfolds

An attacker sends crafted fragmented traffic that triggers act_ct fragment storage and re-assembly; the overwritten skb cb field causes invalid pointers in the fragment rbtree, resulting in a crash during timer-driven cleanup.

How to fix it

Apply the upstream fix that prevents skb cb overwrite when tcf_ct_handle_fragments returns -EINPROGRESS; update to a kernel containing commit resolving CVE-2021-47014.

How to confirm the fix worked

Confirm the patch is present by inspecting net/sched/act_ct.c for the conditional check before restoring qdisc cb; test with re-assembly/re-fragmentation workloads under KASAN.

Typical attack path

  1. Send IP fragments that require re-assembly under act_ct
  2. Trigger tcf_ct_handle_fragments returning -EINPROGRESS
  3. Restore skb qdisc cb with attacker data
  4. Force fragment purge via timer or memory pressure
  5. Trigger wild read in inet_frag_rbtree_purge

How to detect it

Search kernel logs for KASAN wild-memory-access reports mentioning inet_frag_rbtree_purge or act_ct; correlate with high rates of fragmented traffic on interfaces using connection tracking.

What your security team should do

  • Prioritize kernel updates on systems using act_ct with fragmentation
  • Monitor for unexplained kernel oops in inet_frag_rbtree_purge
  • Disable act_ct on untrusted interfaces if patching is delayed

The record

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: fix wild memory access when clearing fragments while testing re-assembly/re-fragmentation using act_ct, it's possible to observe a crash like the following one: KASAN: maybe wild-memory-access in range [0x0001000000000448-0x000100000000044f] CPU: 50 PID: 0 Comm: swapper/50 Tainted: G S 5.12.0-rc7+ #424 Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.4.3 01/17/2017 RIP: 0010:inet_frag_rbtree_purge+0x50/0xc0 Code: 00 fc ff df 48 89 c3 31 ed 48 89 df e8 a9 7a 38 ff 4c 89 fe 48 89 df 49 89 c6 e8 5b 3a 38 ff 48 8d 7b 40 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00 75 59 48 8d bb d0 00 00 00 4c 8b 6b 40 48 89 f8 48 RSP: 0018:ffff888c31449db8 EFLAGS: 00010203 RAX: 0000200000000089 RBX: 000100000000040e RCX: ffffffff989eb960 RDX: 0000000000000140 RSI: ffffffff97cfb977 RDI: 000100000000044e RBP: 0000000000000900 R08: 0000000000000000 R09: ffffed1186289350 R10: 0000000000000003 R11: ffffed1186289350 R12: dffffc0000000000 R13: 000100000000040e R14: 0000000000000000 R15: ffff888155e02160 FS: 0000000000000000(0000) GS:ffff888c31440000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005600cb70a5b8 CR3: 0000000a2c014005 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> inet_frag_destroy+0xa9/0x150 call_timer_fn+0x2d/0x180 run_timer_softirq+0x4fe/0xe70 __do_softirq+0x197/0x5a0 irq_exit_rcu+0x1de/0x200 sysvec_apic_timer_interrupt+0x6b/0x80 </IRQ> when act_ct temporarily stores an IP fragment, restoring the skb qdisc cb results in putting random data in FRAG_CB(), and this causes those "wild" memory accesses later, when the rbtree is purged. Never overwrite the skb cb in case tcf_ct_handle_fragments() returns -EINPROGRESS.

Affected packages

Ecosystem Package Introduced Fixed
Debian:11 linux 0 No fix
Debian:12 linux 0 5.14.6-1
Debian:13 linux 0 5.14.6-1
SUSE:Enterprise Storage 7.1 kernel-64kb 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Enterprise Storage 7.1 kernel-docs 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-obs-build 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-preempt 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-source 0 5.3.18-150300.59.158.1
SUSE:Enterprise Storage 7.1 kernel-syms 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Availability Extension 15 SP3 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-64kb 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-docs 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-obs-build 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-preempt 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-source 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS kernel-syms 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Live Patching 15 SP3 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Live Patching 15 SP3 kernel-livepatch-SLE15-SP3_Update_43 0 1-150300.7.3.5
SUSE:Linux Enterprise Micro 5.1 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Micro 5.1 kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Linux Enterprise Micro 5.1 kernel-rt 0 5.3.18-150300.166.1
SUSE:Linux Enterprise Micro 5.1 kernel-source-rt 0 5.3.18-150300.166.1
SUSE:Linux Enterprise Micro 5.2 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Micro 5.2 kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Linux Enterprise Micro 5.2 kernel-rt 0 5.3.18-150300.166.1
SUSE:Linux Enterprise Micro 5.2 kernel-source-rt 0 5.3.18-150300.166.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-64kb 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-docs 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-obs-build 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-preempt 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-source 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-syms 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server 15 SP3-LTSS kernel-zfcpdump 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-default 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-default-base 0 5.3.18-150300.59.158.1.150300.18.92.5
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-docs 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-obs-build 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-preempt 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-source 0 5.3.18-150300.59.158.1
SUSE:Linux Enterprise Server for SAP Applications 15 SP3 kernel-syms 0 5.3.18-150300.59.158.1
Ubuntu:16.04:LTS linux-hwe-edge 0 No fix
Ubuntu:18.04:LTS linux-aws-5.0 0 No fix
Ubuntu:18.04:LTS linux-aws-5.3 0 No fix
Ubuntu:18.04:LTS linux-azure 0 No fix
Ubuntu:18.04:LTS linux-azure-5.3 0 No fix
Ubuntu:18.04:LTS linux-azure-edge 0 No fix
Ubuntu:18.04:LTS linux-gcp 0 No fix
Ubuntu:18.04:LTS linux-gcp-5.3 0 No fix
Ubuntu:18.04:LTS linux-gke-4.15 0 No fix
Ubuntu:18.04:LTS linux-gke-5.4 0 No fix
Ubuntu:18.04:LTS linux-gkeop-5.4 0 No fix
Ubuntu:18.04:LTS linux-hwe 0 No fix
Ubuntu:18.04:LTS linux-hwe-edge 0 No fix
Ubuntu:18.04:LTS linux-oem 0 No fix
Ubuntu:18.04:LTS linux-oracle-5.0 0 No fix
Ubuntu:18.04:LTS linux-oracle-5.3 0 No fix
Ubuntu:20.04:LTS linux 0 5.4.0-9.12
Ubuntu:20.04:LTS linux-aws 0 5.4.0-1005.5
Ubuntu:20.04:LTS linux-aws-5.11 0 No fix
Ubuntu:20.04:LTS linux-aws-5.13 0 No fix
Ubuntu:20.04:LTS linux-aws-5.15 0 5.15.0-1014.18~20.04.1
Ubuntu:20.04:LTS linux-aws-5.8 0 No fix
Ubuntu:20.04:LTS linux-azure 0 5.4.0-1006.6
Ubuntu:20.04:LTS linux-azure-5.11 0 No fix
Ubuntu:20.04:LTS linux-azure-5.13 0 No fix
Ubuntu:20.04:LTS linux-azure-5.15 0 5.15.0-1007.8~20.04.1
Ubuntu:20.04:LTS linux-azure-5.8 0 No fix
Ubuntu:20.04:LTS linux-azure-fde 0 No fix
Ubuntu:20.04:LTS linux-azure-fde-5.15 0 5.15.0-1019.24~20.04.1.1
Ubuntu:20.04:LTS linux-bluefield 0 No fix
Ubuntu:20.04:LTS linux-bluefield 0 5.4.0-1019.22
Ubuntu:20.04:LTS linux-gcp 0 5.4.0-1005.5
Ubuntu:20.04:LTS linux-gcp-5.11 0 No fix
Ubuntu:20.04:LTS linux-gcp-5.13 0 No fix
Ubuntu:20.04:LTS linux-gcp-5.15 0 5.15.0-1006.9~20.04.1
Ubuntu:20.04:LTS linux-gcp-5.8 0 No fix
Ubuntu:20.04:LTS linux-gke 0 No fix
Ubuntu:20.04:LTS linux-gke-5.15 0 No fix
Ubuntu:20.04:LTS linux-gkeop 0 5.4.0-1008.9
Ubuntu:20.04:LTS linux-gkeop-5.15 0 5.15.0-1003.5~20.04.2
Ubuntu:20.04:LTS linux-hwe-5.11 0 No fix
Ubuntu:20.04:LTS linux-hwe-5.13 0 No fix
Ubuntu:20.04:LTS linux-hwe-5.15 0 5.15.0-33.34~20.04.1
Ubuntu:20.04:LTS linux-hwe-5.8 0 No fix
Ubuntu:20.04:LTS linux-ibm 0 5.4.0-1003.4
Ubuntu:20.04:LTS linux-ibm-5.15 0 5.15.0-1033.36~20.04.1
Ubuntu:20.04:LTS linux-intel-5.13 0 No fix
Ubuntu:20.04:LTS linux-intel-iotg-5.15 0 5.15.0-1003.5~20.04.1
Ubuntu:20.04:LTS linux-iot 0 5.4.0-1001.3
Ubuntu:20.04:LTS linux-kvm 0 5.4.0-1004.4
Ubuntu:20.04:LTS linux-lowlatency-hwe-5.15 0 5.15.0-33.34~20.04.1
Ubuntu:20.04:LTS linux-oem-5.10 0 No fix
Ubuntu:20.04:LTS linux-oem-5.13 0 No fix
Ubuntu:20.04:LTS linux-oem-5.14 0 No fix
Ubuntu:20.04:LTS linux-oem-5.6 0 No fix
Ubuntu:20.04:LTS linux-oracle 0 5.4.0-1005.5
Ubuntu:20.04:LTS linux-oracle-5.11 0 No fix
Ubuntu:20.04:LTS linux-oracle-5.13 0 No fix
Ubuntu:20.04:LTS linux-oracle-5.15 0 5.15.0-1007.9~20.04.1
Ubuntu:20.04:LTS linux-oracle-5.8 0 No fix
Ubuntu:20.04:LTS linux-raspi 0 5.4.0-1007.7
Ubuntu:20.04:LTS linux-raspi2 0 No fix
Ubuntu:20.04:LTS linux-riscv 0 No fix
Ubuntu:20.04:LTS linux-riscv-5.11 0 No fix
Ubuntu:20.04:LTS linux-riscv-5.15 0 5.15.0-1015.17~20.04.1
Ubuntu:20.04:LTS linux-riscv-5.8 0 No fix
Ubuntu:20.04:LTS linux-xilinx-zynqmp 0 5.4.0-1020.24
Ubuntu:22.04:LTS linux 0 5.13.0-19.19
Ubuntu:22.04:LTS linux-allwinner-5.19 0 No fix
Ubuntu:22.04:LTS linux-aws 0 5.13.0-1005.6
Ubuntu:22.04:LTS linux-aws-5.19 0 No fix
Ubuntu:22.04:LTS linux-aws-6.2 0 No fix
Ubuntu:22.04:LTS linux-aws-6.5 0 6.5.0-1008.8~22.04.1
Ubuntu:22.04:LTS linux-azure 0 5.13.0-1006.7
Ubuntu:22.04:LTS linux-azure-5.19 0 No fix
Ubuntu:22.04:LTS linux-azure-6.2 0 No fix
Ubuntu:22.04:LTS linux-azure-6.5 0 6.5.0-1007.7~22.04.1
Ubuntu:22.04:LTS linux-azure-fde 0 5.15.0-1019.24.1
Ubuntu:22.04:LTS linux-azure-fde-5.19 0 No fix
Ubuntu:22.04:LTS linux-azure-fde-6.2 0 No fix
Ubuntu:22.04:LTS linux-gcp 0 5.13.0-1005.6
Ubuntu:22.04:LTS linux-gcp-5.19 0 No fix
Ubuntu:22.04:LTS linux-gcp-6.2 0 No fix
Ubuntu:22.04:LTS linux-gcp-6.5 0 6.5.0-1010.10~22.04.3
Ubuntu:22.04:LTS linux-gke 0 5.15.0-1002.2
Ubuntu:22.04:LTS linux-gkeop 0 5.15.0-1001.2
Ubuntu:22.04:LTS linux-hwe-5.19 0 No fix
Ubuntu:22.04:LTS linux-hwe-6.2 0 No fix
Ubuntu:22.04:LTS linux-hwe-6.5 0 6.5.0-14.14~22.04.1
Ubuntu:22.04:LTS linux-hwe-6.8 0 6.8.0-38.38~22.04.1
Ubuntu:22.04:LTS linux-ibm 0 5.15.0-1002.2
Ubuntu:22.04:LTS linux-intel-iot-realtime 0 No fix
Ubuntu:22.04:LTS linux-intel-iot-realtime 0 5.15.0-1021.26
Ubuntu:22.04:LTS linux-intel-iotg 0 5.15.0-1004.6
Ubuntu:22.04:LTS linux-kvm 0 5.13.0-1004.4
Ubuntu:22.04:LTS linux-lowlatency 0 5.15.0-22.22
Ubuntu:22.04:LTS linux-lowlatency-hwe-5.19 0 No fix
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.2 0 No fix
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.5 0 6.5.0-14.14.1~22.04.1
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.8 0 6.8.0-38.38.1~22.04.2
Ubuntu:22.04:LTS linux-nvidia 0 5.15.0-1005.5
Ubuntu:22.04:LTS linux-nvidia-6.2 0 No fix
Ubuntu:22.04:LTS linux-nvidia-6.5 0 6.5.0-1004.4
Ubuntu:22.04:LTS linux-nvidia-6.8 0 6.8.0-1008.8~22.04.1
Ubuntu:22.04:LTS linux-oem-5.17 0 No fix
Ubuntu:22.04:LTS linux-oem-6.0 0 No fix
Ubuntu:22.04:LTS linux-oem-6.1 0 No fix
Ubuntu:22.04:LTS linux-oem-6.5 0 6.5.0-1003.3
Ubuntu:22.04:LTS linux-oracle 0 5.13.0-1008.10
Ubuntu:22.04:LTS linux-oracle-6.5 0 6.5.0-1013.13~22.04.4
Ubuntu:22.04:LTS linux-raspi 0 5.13.0-1008.9
Ubuntu:22.04:LTS linux-realtime 0 No fix
Ubuntu:22.04:LTS linux-riscv 0 No fix
Ubuntu:22.04:LTS linux-riscv-5.19 0 No fix
Ubuntu:22.04:LTS linux-riscv-6.5 0 6.5.0-17.17.1.1~22.04.1
Ubuntu:22.04:LTS linux-riscv-6.8 0 6.8.0-38.38.1~22.04.1
Ubuntu:22.04:LTS linux-starfive-5.19 0 No fix
Ubuntu:22.04:LTS linux-starfive-6.2 0 No fix
Ubuntu:22.04:LTS linux-starfive-6.5 0 6.5.0-1007.8~22.04.1
Ubuntu:22.04:LTS linux-xilinx-zynqmp 0 5.15.0-1022.26
Ubuntu:22.04:LTS:for:NVIDIA:BlueField linux-bluefield 0 5.15.0-1011.13
Ubuntu:24.04:LTS linux 0 6.5.0-9.9
Ubuntu:24.04:LTS linux-aws 0 6.5.0-1008.8
Ubuntu:24.04:LTS linux-azure 0 6.5.0-1007.7
Ubuntu:24.04:LTS linux-gcp 0 6.5.0-1007.7
Ubuntu:24.04:LTS linux-gke 0 6.8.0-1003.5
Ubuntu:24.04:LTS linux-gkeop 0 6.8.0-1001.3
Ubuntu:24.04:LTS linux-ibm 0 6.5.0-1009.9
Ubuntu:24.04:LTS linux-lowlatency 0 6.5.0-9.9.1
Ubuntu:24.04:LTS linux-nvidia 0 6.8.0-1007.7
Ubuntu:24.04:LTS linux-nvidia-lowlatency 0 6.8.0-1009.9.1
Ubuntu:24.04:LTS linux-oem-6.8 0 6.8.0-1003.3
Ubuntu:24.04:LTS linux-oracle 0 6.5.0-1010.10
Ubuntu:24.04:LTS linux-raspi 0 6.5.0-1005.7
Ubuntu:24.04:LTS linux-raspi-realtime 0 No fix
Ubuntu:24.04:LTS linux-raspi-realtime 0 6.7.0-2001.1
Ubuntu:24.04:LTS linux-realtime 0 6.8.0-1008.19
Ubuntu:24.04:LTS linux-riscv 0 6.5.0-9.9.1
Ubuntu:Pro:16.04:LTS linux-hwe-edge 0 No fix
Ubuntu:Pro:18.04:LTS linux-aws-5.0 0 No fix
Ubuntu:Pro:18.04:LTS linux-aws-5.3 0 No fix
Ubuntu:Pro:18.04:LTS linux-azure 0 No fix
Ubuntu:Pro:18.04:LTS linux-azure-5.3 0 No fix
Ubuntu:Pro:18.04:LTS linux-azure-edge 0 No fix
Ubuntu:Pro:18.04:LTS linux-gcp 0 No fix
Ubuntu:Pro:18.04:LTS linux-gcp-5.3 0 No fix
Ubuntu:Pro:18.04:LTS linux-gke-4.15 0 No fix
Ubuntu:Pro:18.04:LTS linux-gke-5.4 0 No fix
Ubuntu:Pro:18.04:LTS linux-gkeop-5.4 0 No fix
Ubuntu:Pro:18.04:LTS linux-hwe 0 No fix
Ubuntu:Pro:18.04:LTS linux-hwe-edge 0 No fix
Ubuntu:Pro:18.04:LTS linux-oem 0 No fix
Ubuntu:Pro:18.04:LTS linux-oracle-5.0 0 No fix
Ubuntu:Pro:18.04:LTS linux-oracle-5.3 0 No fix

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