CVE-2026-34183: OpenSSL

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

Issue summary: Remote peer may exhaust heap memory of the QUIC server or client by flooding it with packets containing PATH_CHALLENGE frames. Impact summary: A malicious remote peer can cause an unbounded memory allocation which can lead to an abnormal termination of the application acting as a QUIC client or server and a Denial of Service. A remote peer may exhaust heap memory by flooding the local QUIC stack with PATH_CHALLENGE frames. The local QUIC stack allocates a PATH_RESPONSE frame for every PATH_CHALLENGE it receives. The allocated PATH_RESPONSE frame gets freed only when the remote peer acknowledges reception of the PATH_RESPONSE frame which will not be done by a malicious peer. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue. The QUIC stack is outside of OpenSSL FIPS module boundary.

Affected products

• OpenSSL OpenSSL: from 3.4.0, before 3.4.6 (fixed in 3.4.6); from 3.5.0, before 3.5.7 (fixed in 3.5.7); from 3.6.0, before 3.6.3 (fixed in 3.6.3); version 4.0.0 only

Published 2026-06-09. Last modified 2026-07-23.