CVE-2019-20838 : Security Advisory and Response

A subject buffer over-read in JIT occurs in PCRE versions prior to 8.43 when using libpcre, making UTF disabled, and having multiple fixed quantifiers in \X or \R. This issue is related to CVE-2019-20454.

Understanding CVE-2019-20838

What is CVE-2019-20838?

PCRE before version 8.43 allows a subject buffer over-read in Just-In-Time (JIT) when UTF is disabled, and \X or \R has more than one fixed quantifier, which is a critical security vulnerability.

The Impact of CVE-2019-20838

This vulnerability could be exploited by attackers to execute arbitrary code or cause a denial of service (DoS) condition on the affected system.

Technical Details of CVE-2019-20838

Vulnerability Description

The vulnerability lies in libpcre in PCRE versions before 8.43, allowing a subject buffer over-read in JIT when specific conditions are met.

Affected Systems and Versions

Product: Not applicable
Vendor: Not applicable
Versions: PCRE versions prior to 8.43

Exploitation Mechanism

The vulnerability can be exploited by using libpcre, disabling UTF, and having multiple fixed quantifiers in \X or \R.

Mitigation and Prevention

Immediate Steps to Take

Apply the latest security updates provided by the vendor.
Disable JIT in PCRE if not required.
Monitor vendor sources for patches and advisories.

Long-Term Security Practices

Regularly update software and libraries to the latest versions.
Implement strong input validation mechanisms to prevent buffer over-read vulnerabilities.

Patching and Updates

Update PCRE to version 8.43 or later to mitigate the vulnerability.