# CVE-2021-3930: Denial of service in QEMU > A malicious guest can crash the QEMU emulator via an off-by-one error in SCSI device emulation, causing a denial of service. - **Severity:** Medium 6.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 18 Feb 2022 - **Updated:** 3 Aug 2024 - **Also known as:** AZL-8671, DEBIAN-CVE-2021-3930, GHSA-2v9g-p8fq-vvh2, RHSA-2021:5065, UBUNTU-CVE-2021-3930 ## What is CVE-2021-3930? CVE-2021-3930 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 18 Feb 2022. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description An off-by-one error was found in the SCSI device emulation in QEMU. It could occur while processing MODE SELECT commands in mode_sense_page() if the 'page' argument was set to MODE_PAGE_ALLS (0x3f). A malicious guest could use this flaw to potentially crash QEMU, resulting in a denial of service condition. Weakness: CWE-193 (Off-by-one Error) ## Which versions are affected by CVE-2021-3930? It affects 10 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `SLOF` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:20200717-1.gite18ddad8.module+el8.4.0+8855+a9e237a9 | | `hivex` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.3.18-21.module+el8.4.0+11609+2eba841a | | `hivex-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.3.18-21.module+el8.4.0+11609+2eba841a | | `hivex-debugsource` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.3.18-21.module+el8.4.0+11609+2eba841a | | `hivex-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.3.18-21.module+el8.4.0+11609+2eba841a | | `libguestfs` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-bash-completion` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-debugsource` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-gfs2` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-gobject` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-gobject-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-gobject-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-inspect-icons` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-java` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-java-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-java-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-javadoc` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-man-pages-ja` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-man-pages-uk` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-rescue` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-rsync` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-tools` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-tools-c` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-tools-c-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libguestfs-winsupport` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:8.2-2.module+el8.4.0+12717+0b0da9ad | | `libguestfs-xfs` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 1:1.44.0-2.module+el8.4.0+10146+75917d2f | | `libiscsi` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libiscsi-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libiscsi-debugsource` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libiscsi-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libiscsi-utils` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libiscsi-utils-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.18.0-8.module+el8.4.0+8855+a9e237a9 | | `libnbd` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.6.0-3.module+el8.4.0+9856+bbc47853 | | `libnbd-bash-completion` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.6.0-3.module+el8.4.0+9856+bbc47853 | | `libnbd-debuginfo` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.6.0-3.module+el8.4.0+9856+bbc47853 | | `libnbd-debugsource` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.6.0-3.module+el8.4.0+9856+bbc47853 | | `libnbd-devel` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:1.6.0-3.module+el8.4.0+9856+bbc47853 | | `libtpms` | Red Hat:advanced_virtualization:8.4::el8 | All versions | 0:0.7.4-4.20201106git2452a24dab.module+el8.4.0+10596+32ba7df3 | Products: Debian Debian Linux, Qemu Qemu, Redhat Codeready Linux Builder, Redhat Codeready Linux Builder for Ibm Z Systems, Redhat Codeready Linux Builder for Power Little Endian, Redhat Enterprise Linux, Redhat Enterprise Linux Advanced Virtualization Eus, Redhat Enterprise Linux for Ibm Z Systems, Redhat Enterprise Linux for Power Little Endian, Redhat Openstack. ## How do I fix CVE-2021-3930? Apply the vendor's patch. ## Is CVE-2021-3930 being exploited? There is no known exploitation of CVE-2021-3930 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-3930 and fix it if it is affected. What it is: CVE-2021-3930 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 18 Feb 2022. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-3930 in the wild and no public exploit code. Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-3930/ (Markdown: https://insights.sbomify.com/CVE-2021-3930/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3930 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3930 - OSV: https://osv.dev/vulnerability/CVE-2021-3930 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-3930/ Summaries are generated and may contain mistakes; the official description above is the record.