# CVE-2026-102664: ProxySQL: Uninitialized heap read in MySQL compressed packet decompression via zlib path

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

ProxySQL is a proxy for MySQL and its forks, as well as PostgreSQL. Prior to 3.0.10, 3.1.10, and 4.0.10, decompress_mysql_payload() in lib/mysql_data_stream.cpp accepts a zlib stream when uncompress() returns Z_OK without checking that the actual output length equals the attacker-controlled payload_length. An authenticated MySQL client that negotiates compression can overstate payload_length, causing buffer2array() to parse the uninitialized tail of a heap buffer as MySQL packet headers and forward stale data to the backend. Backend error responses can disclose prior SQL queries, result data, credentials, or session state, and malformed lengths can also cause excessive allocations. This issue is fixed in versions 3.0.10, 3.1.10, and 4.0.10.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- sysown / proxysql: < 3.0.10 (affected); >= 3.1.0, < 3.1.10 (affected); >= 4.0.0, < 4.0.10 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 7.1 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-908

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/sysown/proxysql/security/advisories/GHSA-fvch-fpgq-pwfx (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/sysown/proxysql/commit/396c742f7d50b1f479e1157e296ee9d0aff1b724 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sysown/proxysql/commit/a8c1cef4d44c4beea7f6aa21b8a09a7cb8c75520 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sysown/proxysql/releases/tag/v3.0.10 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sysown/proxysql/releases/tag/v3.1.10 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sysown/proxysql/releases/tag/v4.0.10 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-102664; retrieved 2026-11-04; source updated 2026-11-04

Revision: c86282a7cbcba8c896f10998eaa6242d2a4070743aff7b3c4bbe1e55750584cf

Canonical: https://y2.dev/cve/CVE-2026-102664

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