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CVE-2021-3491— Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass

Quick assessment

Affected
Linux Linux kernel
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel MAX_RW_COUNT存在缓冲区错误漏洞。攻击者可以通过Linux内核的MAX_RW_COUNT触发缓冲区溢出，以触发拒绝服务，并可能运行代码。

CVSS 7.8 · High EPSS 0.64% · P49

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation
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I. Basic Information for CVE-2021-3491

Vulnerability Information
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Vulnerability Title
Linux kernel io_uring PROVIDE_BUFFERS MAX_RW_COUNT bypass
Source: CVE Program / CVE List V5
Vulnerability Description
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).
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
缓冲区大小计算不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel MAX_RW_COUNT存在缓冲区错误漏洞。攻击者可以通过Linux内核的MAX_RW_COUNT触发缓冲区溢出，以触发拒绝服务，并可能运行代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux kernel trunk ~ v5.13-rc4 -

II. Public POCs for CVE-2021-3491

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III. Intelligence Information for CVE-2021-3491

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Patches & Fixes for CVE-2021-3491 (1)

Vendor Advisories for CVE-2021-3491 (4)

Mailing List Discussions for CVE-2021-3491 (1)

Same Patch Batch · Linux · 2021-06-04 · 3 CVEs total

CVE-2021-3490 7.8 HIGH Linux kernel eBPF bitwise ops ALU32 bounds tracking
CVE-2021-3489 7.8 HIGH Linux kernel eBPF RINGBUF map oversized allocation

IV. Related Vulnerabilities

Same product: Linux kernel
Same vendor: Linux
Same weakness: CWE-131

V. Comments for CVE-2021-3491

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