HAProxy is a TCP/HTTP reverse proxy for high availability environments.
A boundary error in HAProxy could cause a buffer overflow when header rewriting is enabled and the configuration sets global.tune.bufsize to a value greater than the default (16384 bytes).
A remote attacker could possibly execute arbitrary code with the privileges of the process or cause a Denial of Service condition.
There is no known workaround at this time.
All HAProxy users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-proxy/haproxy-1.4.21"