CVE-2019-19203
Description
An out-of-bounds read vulnerability was found in the way Oniguruma handled regular expressions with GB18030 character encoding. A UChar pointer is dereferenced without checking if it passed the end of the matched string, leading to a heap-based buffer over-read. A remote attacker could abuse this flaw by providing a malformed regular expression that, when processed by an application linked to Oniguruma, might crash the application causing a denial of service.
Statement
This flaw did not affect the versions of Oniguruma (embedded in php) as shipped with Red Hat Enterprise Linux 5, as they did not include support for GB18030 character encoding, which was introduced in a later version of the library.
The versions of Ruby as shipped with Red Hat Enterprise Linux and Red Hat Software Collections 3 do not use Oniguruma but rather Onigmo, a regular expressions library forked from Oniguruma focusing on new expressions supported in Perl 5.10+. Those versions are affected by this flaw because both Onigmo and Oniguruma share the same vulnerable code. However, Ruby does perform additional checks which prevent the vulnerable code path to be easily reached, hence lowering the severity of the flaw.
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 | 7.5 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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.
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