What’s Vulnerable › Vulnerabilities

CVE-2021-20257

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2022-03-16 · updated 2026-06-17
• Weakness: CWE-835

Description

An infinite loop flaw was found in the e1000 NIC emulator of the QEMU. This issue occurs while processing transmits (tx) descriptors in process_tx_desc if various descriptor fields are initialized with invalid values. This flaw allows a guest to consume CPU cycles on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Affected products

• Debian Linux: 10.0
• Fedoraproject Fedora: 33
• QEMU: before 6.2.0 — fixed in 6.2.0
• RedHat Codeready Linux Builder: all versions
• Red Hat Enterprise Linux: 6.0, 8.0
• RedHat Enterprise Linux For Ibm Z Systems: 8.0
• RedHat Enterprise Linux For Power Little Endian: 8.0
• nova_libvirt container provided by the Red Hat OpenStack Platform: 10.0, 13.0

How to fix

Upgrade to a fixed version: QEMU 6.2.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1930087
• https://github.com/qemu/qemu/commit/3de46e6fc489c52c9431a8a832ad8170a7569bd8
• https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
• https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg07428.html
• https://security.gentoo.org/glsa/202208-27
• https://security.netapp.com/advisory/ntap-20220425-0003/
• https://www.openwall.com/lists/oss-security/2021/02/25/2
• https://bugzilla.redhat.com/show_bug.cgi?id=1930087
• https://github.com/qemu/qemu/commit/3de46e6fc489c52c9431a8a832ad8170a7569bd8
• https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
• https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg07428.html
• https://security.gentoo.org/glsa/202208-27

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