AI analysis
OpenSSL’s QUIC stream reassembly slows sharply when stream data arrives out of order. A remote peer that has already completed the handshake can send compliant STREAM frames inside the advertised receive window so that fragment handling degrades to quadratic work in the number of buffered frames, driving connection-scoped CPU use and a potential denial of service with little bandwidth. Integrity and confidentiality are not affected, and the issue is rated medium (CVSS 3.1 5.3) with low availability impact. Anyone running an OpenSSL build that uses this QUIC stack is in scope; the FIPS module is not. There is no public proof of concept and the CVE is not listed in CISA KEV.
What to do: Apply the OpenSSL update from your OS or vendor (Ubuntu trackers reference USN-8861-1) and restart processes that link against the updated library. Until patched, limit which peers can complete a QUIC handshake, and watch QUIC workers for sustained CPU spikes from low-bandwidth connections. The OpenSSL FIPS module is not affected.
Affected
| OpenSSL (QUIC stream reassembly) | — |
Estimated exposure
largeOrder of magnitude: hundreds of thousands to millions of OpenSSL deployments may include the code, but only the smaller QUIC-enabled subset is attackable; a… — OpenSSL is shipped in mainstream Linux distributions (an Ubuntu notice covers this issue) and is embedded across servers, appliances, and applications at very large scale, but only endpoints that actually use OpenSSL’s QUIC stack after a…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
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.