CVE-2026-42772 Affecting openssl package, versions <3.6.5-1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.33% (24th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-OPENSSL-20267517
  • published30 Sept 2026
  • disclosed29 Sept 2026

Introduced: 29 Sep 2026

NewCVE-2026-42772  (opens in a new tab)

How to fix?

Upgrade Debian:unstable openssl to version 3.6.5-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream openssl package and not the openssl package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1