CVE-2026-75804 — QUIC Connection-Level Flow Control is Not Enforced for Streams

Affected: OpenSSL

Issue summary: OpenSSL QUIC stack does not enforce connection level flow control for streams. Remote peers may send more bytes as long as they fit within the stream flow control limits.

Impact summary: A malicious remote peer may exploit the lack of connection flow control for streams to make the QUIC stack receive ~100MB of memory instead of 768 KiB (default flow control window size).

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: The local QUIC stack advertises two flow control limits to its remote peer: stream flow control limit and connection flow control limit. The remote peer must follow both limits when transmitting stream data.

Whenever the local QUIC stack receives a stream frame, it validates that the size of the received stream frame stays within flow control limits. If either limit is exceeded (stream level or connection level), then the QUIC stack must close the connection with a flow control error.

The vulnerable OpenSSL QUIC stack enforces the stream-level but not the connection-level limit. To exploit the issue, three conditions must be met: - the remote peer opens several streams - each stream must stay within the stream-level flow control limit - there must be no zero-offset byte sent on any of the streams (to prevent the vulnerable QUIC stack from consuming data). By meeting the conditions above, the remote peer may make the local stack allocate 2 x MAX_STREAMS x (stream flow control limit) bytes of memory. M…

USN-8847-1 — openssl vulnerabilities

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:26.04:LTS: openssl

It was discovered that OpenSSL incorrectly handled certain certificate revocation list distribution point names. An attacker could possibly use this issue to cause OpenSSL to consume excessive memory, resulting in a denial of service. (CVE-2026-35189)

It was discovered that OpenSSL incorrectly handled QUIC unvalidated amplification credit accounting. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-35191)

It was discovered that OpenSSL incorrectly implemented scalar multiplication for non-NIST elliptic curves. An attacker could possibly use this issue to perform a timing side-channel attack and obtain sensitive information. (CVE-2026-54872)

It was discovered that OpenSSL incorrectly implemented SM2 scalar multiplication on ARM64 and RISC-V architectures. An attacker could possibly use this issue to perform a timing side-channel attack and obtain sensitive information. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-54875)

It was discovered that OpenSSL incorrectly handled SSL context switching during a TLS handshake. An attacker could possibly use this issue to cause an out-of-bounds read, resulting in a denial of service or obtaining sensitive information. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-72897)

It was discovered that OpenSSL incorrectly enforced QUIC connection- level flow control for streams. An attacker could possibly use this issue to cause OpenSSL to consume excess…

Most recent entries from all

CVE-2026-75804 — QUIC Connection-Level Flow Control is Not Enforced for Streams

USN-8847-1 — openssl vulnerabilities