CVE-2019-20433
Description
From CVE.org
libaspell.a in GNU Aspell before 0.60.8 has a buffer over-read for a string ending with a single '\0' byte, if the encoding is set to ucs-2 or ucs-4 outside of the application, as demonstrated by the ASPELL_CONF environment variable.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.8 | 9.1 | N/A |
| Attack Vector | Local | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | High | N/A |
| Integrity Impact | Low | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Red Hat CVSS v3 Score Explanation
This issue is a buffer over-read and it's likely to crash quickly, but could also potentially leak sensitive information or cause integrity problems. As this is a library, network access may technically be possible, but seems relatively far fetched. An attack vector of local nature seems more likely. Additionally, most applications explicitly set their encoding value, which prevents exploitation. Thus, access complexity has been set to high. In a lot of cases attackers would need to be able to change the "ASPELL_CONF" environment variable or aspell config file, so privileges required are set to low.
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability
Technical Impact: Read Memory; Execute Unauthorized Code or Commands
The case of an omitted null character is the most dangerous of the possible issues. This will almost certainly result in information disclosure, and possibly a buffer overflow condition, which may be exploited to execute arbitrary code.
Confidentiality,Integrity,Availability
Technical Impact: DoS: Crash, Exit, or Restart; Read Memory; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
If a null character is omitted from a string, then most string-copying functions will read data until they locate a null character, even outside of the intended boundaries of the string. This could: cause a crash due to a segmentation fault cause sensitive adjacent memory to be copied and sent to an outsider trigger a buffer overflow when the copy is being written to a fixed-size buffer.
Integrity,Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart
Misplaced null characters may result in any number of security problems. The biggest issue is a subset of buffer overflow, and write-what-where conditions, where data corruption occurs from the writing of a null character over valid data, or even instructions. A randomly placed null character may put the system into an undefined state, and therefore make it prone to crashing. A misplaced null character may corrupt other data in memory.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Alter Execution Logic; Execute Unauthorized Code or Commands
Should the null character corrupt the process flow, or affect a flag controlling access, it may lead to logical errors which allow for the execution of arbitrary code.
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