OpenSSL QUIC Heap Exhaustion via PATH_CHALLENGE Flood (before 4.0)
CVE-2026-34183 Published on June 9, 2026
Unbounded Memory Growth in the QUIC PATH_CHALLENGE Handler
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.
Vulnerability Analysis
CVE-2026-34183 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a Stack Exhaustion Vulnerability?
The product manages a group of objects or resources and performs a separate memory allocation for each object, but it does not properly limit the total amount of memory that is consumed by all of the combined objects.
CVE-2026-34183 has been classified to as a Stack Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-34183
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Affected Versions
OpenSSL:- Version 4.0.0 and below 4.0.1 is affected.
- Version 3.6.0 and below 3.6.3 is affected.
- Version 3.5.0 and below 3.5.7 is affected.
- Version 3.4.0 and below 3.4.6 is affected.