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CVE-2021-3490

Status Candidate

Overview

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).

Related Files

Linux eBPF ALU32 32-bit Invalid Bounds Tracking Local Privilege Escalation
Posted Sep 1, 2021
Authored by Grant Willcox, chompie1337, Manfred Paul | Site metasploit.com

Linux kernels from 5.7-rc1 prior to 5.13-rc4, 5.12.4, 5.11.21, and 5.10.37 are vulnerable to a bug in the eBPF verifier's verification of ALU32 operations in the scalar32_min_max_and function when performing AND operations, whereby under certain conditions the bounds of a 32 bit register would not be properly updated. This can be abused by attackers to conduct an out of bounds read and write in the Linux kernel and therefore achieve arbitrary code execution as the root user. The target system must be compiled with eBPF support and not have kernel.unprivileged_bpf_disabled set, which prevents unprivileged users from loading eBPF programs into the kernel. Note that if kernel.unprivileged_bpf_disabled is enabled this module can still be utilized to bypass protections such as SELinux, however the user must already be logged as a privileged user such as root.

tags | exploit, arbitrary, kernel, root, code execution
systems | linux
advisories | CVE-2021-3490
SHA-256 | 72309dfd15f65e29e815be3b1add6fc3b2c2baad6cb3b01ac2bbfff15a8b2c9d
Ubuntu Security Notice USN-4949-1
Posted May 12, 2021
Authored by Ubuntu | Site security.ubuntu.com

Ubuntu Security Notice 4949-1 - Ryota Shiga discovered that the eBPF implementation in the Linux kernel did not properly verify that a BPF program only reserved as much memory for a ring buffer as was allocated. A local attacker could use this to cause a denial of service or execute arbitrary code. Manfred Paul discovered that the eBPF implementation in the Linux kernel did not properly track bounds on bitwise operations. A local attacker could use this to cause a denial of service or execute arbitrary code. Various other issues were also addressed.

tags | advisory, denial of service, arbitrary, kernel, local
systems | linux, ubuntu
advisories | CVE-2020-25639, CVE-2021-26930, CVE-2021-26931, CVE-2021-28375, CVE-2021-29264, CVE-2021-29265, CVE-2021-29266, CVE-2021-29646, CVE-2021-29650, CVE-2021-3489, CVE-2021-3490, CVE-2021-3491
SHA-256 | 76d964fe9c27085f6742f1876c549a9562042eb085a4203978ffafc9d5a92ddc
Ubuntu Security Notice USN-4948-1
Posted May 12, 2021
Authored by Ubuntu | Site security.ubuntu.com

Ubuntu Security Notice 4948-1 - Ryota Shiga discovered that the eBPF implementation in the Linux kernel did not properly verify that a BPF program only reserved as much memory for a ring buffer as was allocated. A local attacker could use this to cause a denial of service or execute arbitrary code. Manfred Paul discovered that the eBPF implementation in the Linux kernel did not properly track bounds on bitwise operations. A local attacker could use this to cause a denial of service or execute arbitrary code. Various other issues were also addressed.

tags | advisory, denial of service, arbitrary, kernel, local
systems | linux, ubuntu
advisories | CVE-2020-25670, CVE-2021-28688, CVE-2021-28951, CVE-2021-28952, CVE-2021-28964, CVE-2021-28971, CVE-2021-28972, CVE-2021-29264, CVE-2021-29266, CVE-2021-29646, CVE-2021-29647, CVE-2021-29649, CVE-2021-29650, CVE-2021-29657, CVE-2021-31916, CVE-2021-3483, CVE-2021-3489, CVE-2021-3490, CVE-2021-3491
SHA-256 | 957eb73e74d19d4c62c7116de0b476cf551491d297e087fb9602eff91b7ee985
Ubuntu Security Notice USN-4950-1
Posted May 12, 2021
Authored by Ubuntu | Site security.ubuntu.com

Ubuntu Security Notice 4950-1 - Ryota Shiga discovered that the eBPF implementation in the Linux kernel did not properly verify that a BPF program only reserved as much memory for a ring buffer as was allocated. A local attacker could use this to cause a denial of service or execute arbitrary code. Manfred Paul discovered that the eBPF implementation in the Linux kernel did not properly track bounds on bitwise operations. A local attacker could use this to cause a denial of service or execute arbitrary code. Various other issues were also addressed.

tags | advisory, denial of service, arbitrary, kernel, local
systems | linux, ubuntu
advisories | CVE-2021-3489, CVE-2021-3490, CVE-2021-3491
SHA-256 | f703c719697ff87020df10163da73587499d3cda884cdd896c4cff9f26e9dda3
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