# CVE-2026-48773: ProxySQL heap overflow in MySQL and PostgreSQL first-packet handling

Source: https://junglewise.ai/threats/cve-2026-48773-proxysql-heap-overflow-in-mysql-and-postgresql-first-packet  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-19. Updated: 2026-06-21  
License: CC BY 4.0 with a link back

CVE-2026-48773 · Severity: critical · CVSS 9.8 · Published 2026-06-19

ProxySQL is a high-performance database proxy used to manage traffic for MySQL and PostgreSQL databases. A critical vulnerability allows an unauthenticated remote attacker to crash the service or potentially execute arbitrary code by sending a specially crafted initial connection packet. This could lead to a complete service outage or unauthorized access to the database infrastructure.

Technologies: [ProxySQL](https://junglewise.ai/threats/technologies/proxysql). Vendors: [ProxySQL](https://junglewise.ai/threats/vendors/proxysql).

## Quick answers

**Is CVE-2026-48773 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-48773 being exploited in the wild.

**How severe is CVE-2026-48773?** Critical severity, with a CVSS score of 9.8, published 19 June 2026.

**Which products and versions are affected?** ProxySQL >= 2.0.18, < 3.0.9.

**Is there a fix for CVE-2026-48773?** A patch was published on 2026-06-04: Version 3.0.9 released with fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-48773 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-48773?** Check whether you run ProxySQL at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based buffer overflow (CWE-787) exists in the MySQL_Data_Stream::read_from_net() and PgSQL_Data_Stream::read_from_net() components of ProxySQL. The vulnerability is rooted in the 'first-read' path where the application reads the initial 4 or 5 bytes of a connection, parses a packet length from the attacker-controlled header, and passes this length directly to a subsequent recv() call. Because the destination buffer (queueIN) is a fixed 32 KB heap-allocated queue, providing a length larger than 32,768 bytes results in an out-of-bounds write. This occurs before any authentication or packet validation takes place. The issue is resolved in version 3.0.9 by bounding the recv() size.

## Affected products

- sysown ProxySQL >= 2.0.18, < 3.0.9

## Timeline

- 2026-05-26: advisory: Internal GHSA advisory published
- 2026-06-04: patched: Version 3.0.9 released with fix
- 2026-06-19: disclosed: Public CVE disclosure

## References

- [https://github.com/sysown/proxysql/releases/tag/v3.0.9](https://github.com/sysown/proxysql/releases/tag/v3.0.9)
- [https://github.com/sysown/proxysql/security/advisories/GHSA-58ww-865x-grpr](https://github.com/sysown/proxysql/security/advisories/GHSA-58ww-865x-grpr)

## Related threats

- [ProxySQL heap buffer over-read in MySQL compression decompression](https://junglewise.ai/threats/cve-2026-102664-proxysql-is-a-proxy-for-mysql-and-its-forks-as-well-as)
- [ProxySQL source IP spoofing and ACL bypass in PROXY protocol v1](https://junglewise.ai/threats/cve-2026-48772-proxysql-source-ip-spoofing-and-acl-bypass-in-proxy-protocol-v1)