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TI-2021-02450 Aliases CVE-2021-3491GHSA-q4c9-gg27-f3pq

Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass

Priority LOW 39CWE-131Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-131 and the CVSS impact.

Summary

The io_uring subsystem in the Linux kernel allowed the MAX_RW_COUNT limit to be bypassed in the PROVIDE_BUFFERS operation, which led to negative values being usedin mem_rw when reading /proc/<PID>/mem. This could be used to create a heap overflow leading to arbitrary code execution in the kernel. It was addressed via commit d1f82808877b ("io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers") (v5.13-rc1) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced in ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS") (v5.7-rc1).

Why it matters now

EPSS 0.00644 51st percentileScored 2026-11-07
Fix Fixed Linux kernel (Linux): v5.13-rc4, v5.12.4, v5.11.21 +1

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux kerneltrunk to before v5.13-rc4; linux-5.12.y to before v5.12.4; linux-5.11.y to before v5.11.21; linux-5.10.y to before v5.10.37; v5.7-rc1 and laterv5.13-rc4, v5.12.4, v5.11.21, v5.10.37Patch availableCNA
  • Linux kernel VendorLinux Affected trunk to before v5.13-rc4; linux-5.12.y to before v5.12.4; linux-5.11.y to before v5.11.21; linux-5.10.y to before v5.10.37; v5.7-rc1 and later Fixed in v5.13-rc4, v5.12.4, v5.11.21, v5.10.37 Patch available CNA

CPE configurations NVD · 4

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*5.7 to before 5.10.37; 5.11 to before 5.11.21; 5.12 to before 5.12.4VulnerableLinux
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*20.04VulnerableCanonical
cpe:2.3:o:canonical:ubuntu_linux:20.10:*:*:*:*:*:*:*20.10VulnerableCanonical
cpe:2.3:o:canonical:ubuntu_linux:21.04:*:*:*:*:*:*:*21.04VulnerableCanonical
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.7 to before 5.10.37; 5.11 to before 5.11.21; 5.12 to before 5.12.4 Vulnerable ·Linux
  • cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:* Versions 20.04 Vulnerable ·Canonical
  • cpe:2.3:o:canonical:ubuntu_linux:20.10:*:*:*:*:*:*:* Versions 20.10 Vulnerable ·Canonical
  • cpe:2.3:o:canonical:ubuntu_linux:21.04:*:*:*:*:*:*:* Versions 21.04 Vulnerable ·Canonical

Remediation

  • Fix · CNA Linux kernel (Linux) Fixed in v5.13-rc4, v5.12.4, v5.11.21, v5.10.37

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Advisory ·

    Linux kernel — ubuntu.com/security/notices/USN-4949-1

    3 records Highest priority Priority MEDIUM 1 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2021-02449 Linux kernel eBPF bitwise ops ALU32 bounds trackingPriority MEDIUM 56
    • TI-2021-02448 Linux kernel eBPF RINGBUF map oversized allocationPriority LOW 35
    Show all 3 records → Advisory →
  • Advisory ·

    Linux kernel — ubuntu.com/security/notices/USN-4950-1

    3 records Highest priority Priority MEDIUM 1 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2021-02449 Linux kernel eBPF bitwise ops ALU32 bounds trackingPriority MEDIUM 56
    • TI-2021-02448 Linux kernel eBPF RINGBUF map oversized allocationPriority LOW 35
    Show all 3 records → Advisory →

Vendor assessments

Red Hat

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

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-2021-3491
  2. 2026-10-03 Alias added: GHSA-q4c9-gg27-f3pq
  3. 2026-10-21 EPSS moved to the 50th–90th percentile

References

Patch 2

Advisory 4

  • 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