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TI-2021-21901 Aliases CVE-2021-47242GHSA-gc8r-vh42-27g4

mptcp: fix soft lookup in subflow_error_report()

Priority LOW 36CWE-667Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-667 and the CVSS impact.

Summary

In the Linux kernel, the following vulnerability has been resolved: mptcp: fix soft lookup in subflow_error_report() Maxim reported a soft lookup in subflow_error_report(): watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:0] RIP: 0010:native_queued_spin_lock_slowpath RSP: 0018:ffffa859c0003bc0 EFLAGS: 00000202 RAX: 0000000000000101 RBX: 0000000000000001 RCX: 0000000000000000 RDX: ffff9195c2772d88 RSI: 0000000000000000 RDI: ffff9195c2772d88 RBP: ffff9195c2772d00 R08: 00000000000067b0 R09: c6e31da9eb1e44f4 R10: ffff9195ef379700 R11: ffff9195edb50710 R12: ffff9195c2772d88 R13: ffff9195f500e3d0 R14: ffff9195ef379700 R15: ffff9195ef379700 FS: 0000000000000000(0000) GS:ffff91961f400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c000407000 CR3: 0000000002988000 CR4: 00000000000006f0 Call Trace: <IRQ> _raw_spin_lock_bh subflow_error_report mptcp_subflow_data_available __mptcp_move_skbs_from_subflow mptcp_data_ready tcp_data_queue tcp_rcv_established tcp_v4_do_rcv tcp_v4_rcv ip_protocol_deliver_rcu ip_local_deliver_finish __netif_receive_skb_one_core netif_receive_skb rtl8139_poll 8139too __napi_poll net_rx_action __do_softirq __irq_exit_rcu common_interrupt </IRQ> The calling function - mptcp_subflow_data_available() - can be invoked from different contexts: - plain ssk socket lock - ssk socket lock + mptcp_data_lock - ssk socket lock + mptcp_data_lock + msk socket lock. Since subflow_error_report() tries to acquire the mptcp_data_lock, the latter two call chains will cause soft lookup. This change addresses the issue moving the error reporting call to outer functions, where the held locks list is known and the we can acquire only the needed one.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00337 27th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.12, 5.12.13, 5.13Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

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

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.11.12 to before 5.125.12Patch availableCNA
LinuxLinux5.12 and later5.12.13, 5.13Patch availableCNA
  • Linux VendorLinux Affected 5.11.12 to before 5.12 Fixed in 5.12 Patch available CNA
  • Linux VendorLinux Affected 5.12 and later Fixed in 5.12.13, 5.13 Patch available CNA

CPE configurations NVD · 7

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*5.11.12 to before 5.12.13VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*5.13 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:*5.13 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:*5.13 rc3VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:*5.13 rc4VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc5:*:*:*:*:*:*5.13 rc5VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.13:rc6:*:*:*:*:*:*5.13 rc6VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.11.12 to before 5.12.13 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:* Versions 5.13 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:* Versions 5.13 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:* Versions 5.13 rc3 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:* Versions 5.13 rc4 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc5:*:*:*:*:*:* Versions 5.13 rc5 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.13:rc6:*:*:*:*:*:* Versions 5.13 rc6 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.12
  • Fix · CNA Linux (Linux) Fixed in 5.12.13, 5.13

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Enterprise Linux 8AffectedNo fix yet
Not affected: 3 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47242
  2. 2026-10-03 Alias added: GHSA-gc8r-vh42-27g4

References

Patch 2

  • 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