CVE-2026-42772
Potential CPU DoS via O(n^2) Fragment Reassembly in QUIC
- State
- Published
- Severity
- 5.3 Medium
- Published
- Sep 29, 2026
- Updated
- Sep 30, 2026
- Reserved
- Apr 29, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | CISA-ADP |
Weaknesses
- CWE-407 Inefficient Algorithmic Complexity
Affected Products
| Product | Versions |
|---|---|
OpenSSLOpenSSL |
|
References
- OpenSSL Advisoryvendor-advisory
- 4.0.3 git commitpatch
- 3.6.5 git commitpatch
- 3.5.9 git commitpatch
- 3.4.8 git commitpatch
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