CVE-2024-35871
Vulnerability Scoring
Status: Awaiting Analysis
Last updated: 🕘 21 Nov 2024, 09:21 UTC
Originally published on: 🕘 19 May 2024, 09:15 UTC
Time between publication and last update: 186 days
CVSS Release:
CVE-2024-35871: In the Linux kernel, the following vulnerability has been resolved: riscv: process: Fix kernel gp leakage childregs represents the registers which are active for the new thread in user context. For a kernel thread, childregs->gp is never used since the kernel gp is not touched by switch_to. For a user mode helper, the gp value can be observed in user space after execve or possibly by other means. [From the email thread] The /* Kernel thread */ comment is somewhat inaccurate in that it is also used for user_mode_helper threads, which exec a user process, e.g. /sbin/init or when /proc/sys/kernel/core_pattern is a pipe. Such threads do not have PF_KTHREAD set and are valid targets for ptrace etc. even before they exec. childregs is the *user* context during syscall execution and it is observable from userspace in at least five ways: 1. kernel_execve does not currently clear integer registers, so the starting register state for PID 1 and other user processes started by the kernel has sp = user stack, gp = kernel __global_pointer$, all other integer registers zeroed by the memset in the patch comment. This is a bug in its own right, but I'm unwilling to bet that it is the only way to exploit the issue addressed by this patch. 2. ptrace(PTRACE_GETREGSET): you can PTRACE_ATTACH to a user_mode_helper thread before it execs, but ptrace requires SIGSTOP to be delivered which can only happen at user/kernel boundaries. 3. /proc/*/task/*/syscall: this is perfectly happy to read pt_regs for user_mode_helpers before the exec completes, but gp is not one of the registers it returns. 4. PERF_SAMPLE_REGS_USER: LOCKDOWN_PERF normally prevents access to kernel addresses via PERF_SAMPLE_REGS_INTR, but due to this bug kernel addresses are also exposed via PERF_SAMPLE_REGS_USER which is permitted under LOCKDOWN_PERF. I have not attempted to write exploit code. 5. Much of the tracing infrastructure allows access to user registers. I have not attempted to determine which forms of tracing allow access to user registers without already allowing access to kernel registers.
The exploitability of CVE-2024-35871 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
No exploitability data is available for CVE-2024-35871.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2024-35871, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2024-35871, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
The EPSS score estimates the probability that this vulnerability will be exploited in the near future.
EPSS Score: 0.044% (probability of exploit)
EPSS Percentile: 12.8%
(lower percentile = lower relative risk)
This vulnerability is less risky than approximately 87.2% of others.
Unknown
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