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CVE-2026-42772

Potential CPU DoS via O(n^2) Fragment Reassembly in QUIC

Published: 9/29/2026 Last updated: 9/30/2026 Reserved: 4/29/2026

Issue summary: The QUIC stream reassembly algorithm performance deteriorates progressively as packets are arriving out of order. The worst case has a quadratic complexity proportional to the number of stream frames kept in the buffer for the received stream data. Impact summary: A remote QUIC peer that completes the handshake can create a connection-scoped CPU pressure and potentially a Denial of Service using compliant STREAM frames inside the advertised receive window, with low attacker bandwidth. CWE: CWE-407: Inefficient Algorithmic Complexity Description: OpenSSL manages received QUIC stream fragments using a doubly-linked list. While it optimizes for append operations (at the end of the list), it falls back to a head-to-tail linear search for any fragment that does not immediately follow the current `tail`. By manipulating the sequence of offsets, an attacker can force the server to perform O(n^2) operations, consuming excessive CPU time for the QUIC process. FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

CNA assigner: openssl (3a12439a-ef3a-4c79-92e6-6081a721f1e5) Requested by: n/a

Metrics

Version Score Severity Vector String
3.1 5.3 Medium CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Opam packages affected (6)

conf-libcurl conf-libssl conf-mingw-w64-openssl-i686 conf-mingw-w64-openssl-x86_64 conf-openssl conf-srt-openssl

Products affected (0)

No product listed.

References (5)

Credits (3)