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Pre-auth heap overflow in ProxySQL first-packet handling

IdentifiersCVE-2026-48773CWE-787

CVE-2026-48773 is a critical pre-authentication heap memory corruption vulnerability in ProxySQL affecting versions 2.0.18 through 3.0.8. The flaw is in the MySQL and PostgreSQL protocol first-read/first-packet handling paths. A remote unauthenticated client can declare an oversized initial packet length, and ProxySQL uses that attacker-controlled length directly in recv() while receiving data into a fixed 32 KB input queue. This can cause a heap-based buffer overflow before authentication is completed.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation can trigger heap memory corruption in a network-facing pre-authentication code path. Because the flaw is remotely reachable without authentication or user interaction and is rated critical (CVSS 9.8), impact can include process crash and denial of service, and potentially arbitrary code execution with the privileges of the ProxySQL process. The associated CVSS impact metrics indicate high confidentiality, integrity, and availability impact.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure of ProxySQL listener ports to only trusted clients and networks, especially any Internet-reachable or untrusted segments, because exploitation is pre-authentication and network-based. Apply network ACLs/firewall restrictions in front of ProxySQL and monitor for malformed or oversized initial MySQL/PostgreSQL connection packets. These are compensating controls only; the definitive mitigation is upgrading to a fixed version.

Remediation

Patch, then assume compromise.

Upgrade ProxySQL to a fixed release. The provided content states that version 3.0.9 patches the issue by bounding the first-packet recv() on both MySQL and PostgreSQL protocols. Additional content indicates fixes were also shipped in builds 3.1.9 and 4.0.9. Validate that the deployed instance is no longer running an affected version (2.0.18 through 3.0.8) and confirm the patched build is installed.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

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Detection signatures

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Social activity6

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