Multiple security issues were discovered in QEMU, a fast processor emulator, which could result in denial of service or the execution of arbitrary code.
For the stable distribution (bullseye), this problem has been fixed in version 1:5.2+dfsg-11+deb11u2.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/