CVE-2020-29443
Description
An out-of-bounds read-access flaw was found in the ATAPI Emulator of QEMU. This issue occurs while processing the ATAPI read command if the logical block address(LBA) is set to an invalid value. A guest user may use this flaw to crash the QEMU process on the host resulting in a denial of service.
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 | 3.9 | 3.9 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | High | High | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:L/I:N/A:L
NVD: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:L/I:N/A:L
Red Hat CVSS v3 Score Explanation
Above scores differ in
AC:H - Because it's difficult to build the reproducer with due inputs to trigger this issue.
PR:H - Because given reproducer uses a kernel module and ioport access to trigger this issue, both require administrative access inside a guest.
C:L - Because it may lead to guest user reading host bytes before the QEMU process crash.
A:L - Because it may resulting in crashing a QEMU process on the host, so its impact is limited to a guest.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
Acknowledgements
Red Hat would like to thank Wenxiang Qian (Tencent Blade Team) for reporting this issue.
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