CVE-2018-12126: Infoleak
A flaw was found in many Intel microprocessor designs related to possible information leak of the processor store buffer structure which contains recent stores (writes) to memory..
Modern Intel microprocessors implement hardware-level micro-optimizations to improve the performance of writing data back to CPU caches. The write operation is split into STA (STore Address) and STD (STore Data) sub-operations. These sub-operations allow the processor to hand-off address generation logic into these sub-operations for optimized writes. Both of these sub-operations write to a shared distributed processor structure called the 'processor store buffer'.
The processor store buffer is conceptually a table of address, value, and 'is valid' entries. As the sub-operations can execute independently of each other, they can each update the address, and/or value columns of the table independently. This means that at different points in time the address or value may be invalid.
The processor may speculatively forward entries from the store buffer. The split design used allows for such forwarding to speculatively use stale values, such as the wrong address, returning data from a previous unrelated store. Since this only occurs for loads that will be reissued following the fault/assist resolution, the program is not architecturally impacted, but store buffer state can be leaked to malicious code carefully crafted to retrieve this data via side-channel analysis.
The processor store buffer entries are equally divided between the number of active Hyper-Threads. Conditions such as power-state change can reallocate the processor store buffer entries in a half-updated state to another thread without ensuring that the entries have been cleared.
Additional information: https://access.redhat.com/security/vulnerabilities/mds
Upstream fixes: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa4bff165070dc40a3de35b78e4f8da8e8d85ec5
Intel Advisory: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00233.html
Other sources
Microarchitectural Store Buffer Data Sampling (MSBDS): Store buffers on some microprocessors utilizing speculative execution may allow an authenticated user to potentially enable information disclosure via a side channel with local access. A list of impacted products can be found here: https://www.intel.com/content/dam/www/public/us/en/documents/corporate-information/SA00233-microcode-update-guidance05132019.pdf
— Launchpad
Microcode. Multiple information disclosure issues were addressed partially by updating the microcode and changing the OS scheduler to isolate the system from web content running in the browser. To completely address these issues, there are additional opt-in mitigations to disable hyper threading and enable microcode-based mitigations for all processes by default. Details of the mitigations can be found at https://support.apple.com/kb/HT210107.
Credit
Affected Software
Remediation
Event History
Peer vulnerabilities
Found alongside the following vulnerabilities.
- CVE-2019-8603
- CVE-2019-8635
- CVE-2019-8590
- CVE-2019-8640
- CVE-2019-2102
- CVE-2019-8592
- CVE-2019-8585
- CVE-2019-8582
- CVE-2019-8589
- CVE-2019-8560
- CVE-2019-8634
- CVE-2019-8616
- CVE-2019-8629
- CVE-2018-4456
- CVE-2019-8606
- CVE-2019-8633
- CVE-2019-8525
- CVE-2019-8547
- CVE-2019-8576
- CVE-2019-8591
- CVE-2019-8573
- CVE-2019-8631
- CVE-2018-12126
- CVE-2018-12127
- CVE-2018-12130
- CVE-2019-11091
- CVE-2019-8604
- CVE-2019-8577
- CVE-2019-8600
- CVE-2019-8598
- CVE-2019-8602
- CVE-2019-8568
- CVE-2019-8574
- CVE-2019-8569
- CVE-2019-6237
- CVE-2019-8571
- CVE-2019-8583
- CVE-2019-8584
- CVE-2019-8586
- CVE-2019-8587
- CVE-2019-8594
- CVE-2019-8595
- CVE-2019-8596
- CVE-2019-8597
- CVE-2019-8601
- CVE-2019-8608
- CVE-2019-8609
- CVE-2019-8610
- CVE-2019-8611
- CVE-2019-8615
- CVE-2019-8619
- CVE-2019-8622
- CVE-2019-8623
- CVE-2019-8628
- CVE-2019-8607
- CVE-2019-8612
Frequently Asked Questions
What is the severity of CVE-2018-12126?
CVE-2018-12126 is considered a medium severity vulnerability affecting Intel microprocessor designs.
How do I fix CVE-2018-12126?
To mitigate CVE-2018-12126, users should update to the latest microcode provided by Intel and apply any relevant software updates from their operating system vendors.
What types of systems are affected by CVE-2018-12126?
CVE-2018-12126 impacts various Intel microprocessors, along with operating systems like macOS, Fedora, and Debian.
What does CVE-2018-12126 exploit?
CVE-2018-12126 exploits an information leak in the processor's store buffer, which can lead to unintended data exposure.
Is CVE-2018-12126 related to other vulnerabilities?
Yes, CVE-2018-12126 is part of a broader group of vulnerabilities affecting Intel's architecture, often categorized under speculative execution vulnerabilities.