Affected: OpenSSL

Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in its unvalidated credit computation, leading to a violation of the RFC 9000 unvalidated connection amplification limit of 3 times the amount of data received.

Impact summary: A remote attacker able to spoof packets to a server using the OpenSSL QUIC implementation might use the server for an amplification of a DDoS attack.

CWE: CWE-440: Expected Behavior Violation

Description: OpenSSL's QUIC stack, when operating as a server, enforces client address validation (RFC 9000, Section 8), to confirm the peer address is not used for a traffic amplification attack. If this feature is disabled on the server, the QUIC stack limits the amount of server data that can be sent to 3 times the amount of data received from the peer address, until such time as the TLS handshake is completed.

The OpenSSL QUIC server, when operating in non-validation mode, adds the length of the whole datagram received to the unvalidated credit limit when processing each QUIC packet in the datagram. A remote peer may, after establishing a connection with an initial client hello frame, send a subsequent datagram containing multiple QUIC packets, leading the server to account the entire datagram length for each packet in the datagram, resulting in the server believing that the peer has sent more data than it actually has, thereby violating the 3x amplification l…

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…