CVE-2021-3490 - CVE House
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Status published High CVE-2021-3490

Linux kernel eBPF bitwise ops ALU32 bounds tracking

Vulnerability Description

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • Manfred Paul (@_manfp) of the RedRocket CTF team (@redrocket_ctf) working with Trend Micro's Zero Day Initiative

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Affected Vendor

Affected Software

Linux kernel
Vulnerable Versions:
trunk, linux-5.12.y, linux-5.11.y, linux-5.10.y, v5.7-rc1

Timeline

Official Publish: June 4th, 2021
Last Modified: September 16th, 2024
Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Weaknesses (CWE)

CWE-787 CWE-20

MITRE ATT&CK TTPs

T1190 Exploit Public-Facing Application
Initial Access
T1068 Exploitation for Privilege Escalation
Privilege Escalation
T1055 Process Injection
Defense Evasion
T1105 Ingress Tool Transfer
Command and Control
T1485 Data Destruction
Impact
T1059 Command and Scripting Interpreter
Execution
T1213 Data from Information Repositories
Collection
T1565.002 Stored Data Manipulation
Impact