Linux Distros 未修补的漏洞: CVE-2021-4440
high Nessus 插件 ID 224247
语言：
简介
Linux/Unix 主机上安装的一个或多个程序包存在漏洞，但供应商表示不会修补此漏洞。描述
Linux/Unix 主机中安装的一个或多个程序包受到一个漏洞影响，而供应商没有提供补丁程序。- 在 Linux 内核中，已解决以下漏洞： x86/xen: Drop USERGS_SYSRET64 paravirt call commit afd30525a659ac0ae0904f0cb4a2ca75522c3123 upstream. USERGS_SYSRET64 is used to return from a syscall via SYSRET, but a Xen PV guest will nevertheless use the IRET hypercall, as there is no sysret PV hypercall defined. So instead of testing all the prerequisites for doing a sysret and then mangling the stack for Xen PV again for doing an iret just use the iret exit from the beginning. This can easily be done via an ALTERNATIVE like it is done for the sysenter compat case already. It should be noted that this drops the optimization in Xen for not restoring a few registers when returning to user mode, but it seems as if the saved instructions in the kernel more than compensate for this drop (a kernel build in a Xen PV guest was slightly faster with this patch applied). While at it remove the stale sysret32 remnants. [pawan: Brad Spengler and Salvatore Bonaccorso <[email protected]> reported a problem with the 5.10 backport commit edc702b4a820 (x86/entry_64: Add VERW just before userspace transition). When CONFIG_PARAVIRT_XXL=y, CLEAR_CPU_BUFFERS is not executed in syscall_return_via_sysret path as USERGS_SYSRET64 is runtime patched to: .cpu_usergs_sysret64 = { 0x0f, 0x01, 0xf8, 0x48, 0x0f, 0x07 }, // swapgs; sysretq which is missing CLEAR_CPU_BUFFERS. It turns out dropping USERGS_SYSRET64 simplifies the code, allowing CLEAR_CPU_BUFFERS to be explicitly added to syscall_return_via_sysret path. Below is with CONFIG_PARAVIRT_XXL=y and this patch applied: syscall_return_via_sysret: ... <+342>: swapgs <+345>: xchg %ax,%ax <+347>: verw -0x1a2(%rip) <------ <+354>: sysretq ] (CVE-2021-4440)
请注意，Nessus 依赖供应商报告的程序包是否存在进行判断。
解决方案
目前尚未有任何已知的解决方案。插件详情
严重性: High
ID: 224247
文件名: unpatched_CVE_2021_4440.nasl
版本: 1.1
类型: local
代理: unix
系列: Misc.
发布时间: 2025/3/5
最近更新时间: 2025/3/5
支持的传感器: Nessus Agent, Nessus
风险信息
VPR
风险因素: High
分数: 7.3
CVSS v2
风险因素: Low
基本分数: 3.2
时间分数: 2.4
矢量: CVSS2#AV:L/AC:L/Au:S/C:P/I:N/A:P
CVSS 分数来源: CVE-2021-4440
CVSS v3
风险因素: High
基本分数: 8.8
时间分数: 7.7
矢量: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
时间矢量: CVSS:3.0/E:U/RL:O/RC:C
漏洞信息
必需的 KB 项: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched
易利用性: No known exploits are available
漏洞发布日期: 2024/6/25
参考资料信息
CVE: CVE-2021-4440