CVE-2021-47607
Kernel exploitation through pointer leakage in Juniper Networks BPF CMPXCHG
Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix kernel address leakage in atomic cmpxchg's r0 aux reg The implementation of BPF_CMPXCHG on a high level has the following parameters: .-[old-val] .-[new-val] BPF_R0 = cmpxchg{32,64}(DST_REG + insn->off, BPF_R0, SRC_REG) `-[mem-loc] `-[old-val] Given a BPF insn can only have two registers (dst, src), the R0 is fixed and used as an auxilliary register for input (old value) as well as output (returning old value from memory location). While the verifier performs a number of safety checks, it misses to reject unprivileged programs where R0 contains a pointer as old value. Through brute-forcing it takes about ~16sec on my machine to leak a kernel pointer with BPF_CMPXCHG. The PoC is basically probing for kernel addresses by storing the guessed address into the map slot as a scalar, and using the map value pointer as R0 while SRC_REG has a canary value to detect a matching address. Fix it by checking R0 for pointers, and reject if that's the case for unprivileged programs.
INFO
Published Date :
June 19, 2024, 3:15 p.m.
Last Modified :
Nov. 21, 2024, 6:36 a.m.
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Remotely Exploitable :
No
Impact Score :
3.6
Exploitability Score :
1.8
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2021-47607.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2021-47607 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2021-47607 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 21, 2024
Action Type Old Value New Value Added Reference https://git.kernel.org/stable/c/a82fe085f344ef20b452cd5f481010ff96b5c4cd Added Reference https://git.kernel.org/stable/c/f87a6c160ecc8c7b417d25f508d3f076fe346136 -
Initial Analysis by [email protected]
Oct. 31, 2024
Action Type Old Value New Value Added CVSS V3.1 NIST AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Changed Reference Type https://git.kernel.org/stable/c/a82fe085f344ef20b452cd5f481010ff96b5c4cd No Types Assigned https://git.kernel.org/stable/c/a82fe085f344ef20b452cd5f481010ff96b5c4cd Patch Changed Reference Type https://git.kernel.org/stable/c/f87a6c160ecc8c7b417d25f508d3f076fe346136 No Types Assigned https://git.kernel.org/stable/c/f87a6c160ecc8c7b417d25f508d3f076fe346136 Patch Added CWE NIST NVD-CWE-noinfo Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.12 up to (excluding) 5.15.11 *cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.16:rc5:*:*:*:*:*:* -
CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jun. 19, 2024
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: bpf: Fix kernel address leakage in atomic cmpxchg's r0 aux reg The implementation of BPF_CMPXCHG on a high level has the following parameters: .-[old-val] .-[new-val] BPF_R0 = cmpxchg{32,64}(DST_REG + insn->off, BPF_R0, SRC_REG) `-[mem-loc] `-[old-val] Given a BPF insn can only have two registers (dst, src), the R0 is fixed and used as an auxilliary register for input (old value) as well as output (returning old value from memory location). While the verifier performs a number of safety checks, it misses to reject unprivileged programs where R0 contains a pointer as old value. Through brute-forcing it takes about ~16sec on my machine to leak a kernel pointer with BPF_CMPXCHG. The PoC is basically probing for kernel addresses by storing the guessed address into the map slot as a scalar, and using the map value pointer as R0 while SRC_REG has a canary value to detect a matching address. Fix it by checking R0 for pointers, and reject if that's the case for unprivileged programs. Added Reference kernel.org https://git.kernel.org/stable/c/f87a6c160ecc8c7b417d25f508d3f076fe346136 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/a82fe085f344ef20b452cd5f481010ff96b5c4cd [No types assigned]
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2021-47607 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2021-47607
weaknesses.