High advisory for h2o

Advisory overview

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 48b7ae12107fd2b118e4641da49599e9aac8edd8, H2O's access-log formatter could write past its log-line buffer when an affected custom access-log format was configured. The allocation errors affected %{error}x, %q when the query string was empty, and numeric elements whose temporary terminating NUL reached the end of the buffer. A matching request could crash the server, while the effect of the one-byte NUL overwrite beyond a crash was not established. This vulnerability is fixed with commit 48b7ae12107fd2b118e4641da49599e9aac8edd8.

Related references

• https://github.com/h2o/h2o/commit/48b7ae12107fd2b118e4641da49599e9aac8edd8
• https://github.com/h2o/h2o/pull/3757
• https://github.com/h2o/h2o/security/advisories/GHSA-m998-r5ww-rqjf