# CVE-2021-26937: Memory corruption in n/a > Remote attackers can cause a denial of service in GNU Screen via crafted UTF-8 sequences, leading to application crashes. - **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 9 Feb 2021 - **Updated:** 9 May 2025 - **Also known as:** ALPINE-CVE-2021-26937, AZL-7356, CLSA-2021-1618497131, CLSA-2021-1634925515, DEBIAN-CVE-2021-26937, DLA-2570-1, DSA-4861-1, GHSA-pjrj-fmxp-cmc4, MGASA-2021-0109, OESA-2021-1090, RHSA-2021:0742, RHSA-2022:1074, SUSE-SU-2021:0491-1, SUSE-SU-2021:0492-1, UBUNTU-CVE-2021-26937, USN-4747-1, USN-4747-2, openSUSE-SU-2021:0304-1, openSUSE-SU-2024:11884-1 ## What is CVE-2021-26937? CVE-2021-26937 is a critical memory corruption vulnerability in Debian Debian Linux, published on 9 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a denial of service (invalid write access and application crash) or possibly have unspecified other impact via a crafted UTF-8 character sequence. Weakness: CWE-88 (Improper Neutralization of Argument Delimiters in a Command) ## Which versions are affected by CVE-2021-26937? It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `screen` | Red Hat:enterprise_linux:7::client | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen` | Red Hat:enterprise_linux:7::server | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen` | Red Hat:enterprise_linux:7::workstation | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen-debuginfo` | Red Hat:enterprise_linux:7::workstation | All versions | 0:4.1.0-0.27.20120314git3c2946.el7_9 | | `screen` | Red Hat:rhel_aus:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen-debuginfo` | Red Hat:rhel_aus:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen` | Red Hat:rhel_e4s:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen-debuginfo` | Red Hat:rhel_e4s:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen` | Red Hat:rhel_tus:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen-debuginfo` | Red Hat:rhel_tus:7.7::server | All versions | 0:4.1.0-0.25.20120314git3c2946.el7_7.1 | | `screen` | SUSE:Enterprise Storage 6 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:HPE Helion OpenStack 8 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise High Performance Computing 15-ESPOS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise High Performance Computing 15-LTSS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP2-BCL | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP2-LTSS | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP3-BCL | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP3-LTSS | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP4-LTSS | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server 15 SP1-BCL | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Server 15 SP1-LTSS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Server 15-LTSS | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP2 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP4 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 15 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Linux Enterprise Server for SAP Applications 15 SP1 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Manager Proxy 4.0 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Manager Retail Branch Server 4.0 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:Manager Server 4.0 | All versions | 4.6.2-5.3.1 | | `screen` | SUSE:OpenStack Cloud 7 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:OpenStack Cloud 8 | All versions | 4.0.4-23.6.1 | | `screen` | SUSE:OpenStack Cloud 9 | All versions | 4.0.4-23.6.1 | Products: Debian Debian Linux, Fedoraproject Fedora, Gnu Screen. ## How do I fix CVE-2021-26937? Apply the vendor's patch. ## Is CVE-2021-26937 being exploited? There is no known exploitation of CVE-2021-26937 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-2021-26937 and fix it if it is affected. What it is: CVE-2021-26937 is a critical memory corruption vulnerability in Debian Debian Linux, published on 9 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-26937 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-2021-26937/ (Markdown: https://insights.sbomify.com/CVE-2021-26937/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26937 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26937 - OSV: https://osv.dev/vulnerability/CVE-2021-26937 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-26937/ Summaries are generated and may contain mistakes; the official description above is the record.