CVE-2018-1000199
Description
An address corruption flaw was discovered in the Linux kernel built with hardware breakpoint (CONFIG_HAVE_HW_BREAKPOINT) support. While modifying a h/w breakpoint via 'modify_user_hw_breakpoint' routine, an unprivileged user/process could use this flaw to crash the system kernel resulting in DoS OR to potentially escalate privileges on a the system.
Statement
This issue does not affect the versions of Linux kernel as shipped with Red Hat Enterprise Linux 5 and Red Hat Enterprise Linux 6.
This issue affects the version of the kernel package as shipped with Red Hat Enterprise Linux 7 and Red Hat Enterprise MRG 2. Future kernel updates for Red Hat Enterprise Linux 7 and Red Hat Enterprise MRG 2 may address this issue.
Mitigation
To mitigate this issue:
1) Save the following script in a 'CVE-2018-1000199.stp' file.
---
probe kernel.function("ptrace_set_debugreg") {
if ($n < 4)
$n = 4; /* set invalid debug register #, returns -EIO */
}
probe begin {
printk(0, "CVE-2018-1000199 mitigation loaded")
}
probe end {
printk(0, "CVE-2018-1000199 mitigation unloaded")
}
---
2) Install systemtap package and its dependencies
# yum install -y systemtap systemtap-runtime
# yum install -y kernel-devel kernel-debuginfo kernel-debuginfo-common
3) Build the mitigation kernel module as root.
# stap -r `uname -r` -m cve_2018_1000199.ko -g CVE-2018-1000199.stp -p4
4) Load the mitigation module as root
# staprun -L cve_2018_1000199.ko
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.8 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Unchanged | N/A |
| Confidentiality | High | None | N/A |
| Integrity Impact | High | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
The code could be left in a bad state.
Acknowledgements
Red Hat would like to thank Andy Lutomirski for reporting this issue.
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