h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. The QUIC stack (quicly), as used by H2O up to commit 43f86e5 (in version 2.3.0-beta and prior), is susceptible to a state exhaustion attack. When H2O is serving HTTP/3, a remote attacker can exploit this vulnerability to progressively increase the memory retained by the QUIC stack. This can eventually cause H2O to abort due to memory exhaustion. The vulnerability has been resolved in commit d67e81d03be12a9d53dc8271af6530f40164cd35. HTTP/1 and HTTP/2 are not affected by this vulnerability as they do not use QUIC. Administrators looking to mitigate this issue without upgrading can disable HTTP/3 support.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. In version 2.3.0-beta2 and prior, when h2o is configured to listen to multiple addresses or ports with each of them using different backend servers managed by multiple entities, a malicious backend entity that also has the opportunity to observe or inject packets exchanged between the client and h2o may misdirect HTTPS requests going to other backends and observe the contents of that HTTPS request being sent. The attack involves a victim client trying to resume a TLS connection and an attacker redirecting the packets to a different address or port than that intended by the client. The attacker must already have been configured by the administrator of h2o to act as a backend to one of the addresses or ports that the h2o instance listens to. Session IDs and tickets generated by h2o are not bound to information specific to the server address, port, or the X.509 certificate, and therefore it is possible for an attacker t…

A LogoFAIL issue was discovered in BmpDecoderDxe in Insyde InsydeH2O with kernel 5.2 before 05.28.47, 5.3 before 05.37.47, 5.4 before 05.45.47, 5.5 before 05.53.47, and 5.6 before 05.60.47 for certain Lenovo devices. Image parsing of crafted BMP logo files can copy data to a specific address during the DXE phase of UEFI execution. This occurs because of an integer signedness error involving PixelHeight and PixelWidth during RLE4/RLE8 compression.

A Local File Inclusion (LFI) vulnerability exists in the h2o-3 REST API, allowing unauthenticated remote attackers to read arbitrary files on the server with the permissions of the user running the h2o-3 instance. This issue affects the default installation and does not require user interaction. The vulnerability can be exploited by making specific GET or POST requests to the ImportFiles and ParseSetup endpoints, respectively. This issue was identified in version 3.40.0.4 of h2o-3.

H2O included a reference to an S3 bucket that no longer existed allowing an attacker to take over the S3 bucket URL.

H2O is vulnerable to stored XSS vulnerability which can lead to a Local File Include attack.

An attacker is able to gain remote code execution on a server hosting the H2O dashboard through it's POJO model import feature.

An SMM memory corruption vulnerability in the SMM driver (SMRAM write) in CsmInt10HookSmm in Insyde InsydeH2O with kernel 5.0 through 5.5 allows attackers to send arbitrary data to SMM which could lead to privilege escalation.

An issue was discovered in IhisiServicesSmm in Insyde InsydeH2O with kernel 5.0 through 5.5. There are arbitrary calls to SetVariable with unsanitized arguments in the SMI handler.

A stack buffer overflow vulnerability discovered in AsfSecureBootDxe in Insyde InsydeH2O with kernel 5.0 through 5.5 allows attackers to run arbitrary code execution during the DXE phase.