# CVE-2026-5450: scanf %mc off-by-one heap buffer overflow > A heap buffer overflow in glibc's scanf function allows attackers to execute arbitrary code or cause denial of service via crafted input. - **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:** 20 Apr 2026 - **Updated:** 15 Oct 2026 - **Also known as:** ALSA-2026:33092, ALSA-2026:33126, ALSA-2026:33226, AZL-83093, CLSA-2026-1782488061, DEBIAN-CVE-2026-5450, ECHO-56eb-505f-7a61, GHSA-v898-xg3c-w4rj, MINI-7hwm-hwwm-72w6, MINI-cmmm-vp98-cjhp, MINI-xvmv-4xrg-gv25, RHSA-2026:33092, RHSA-2026:33126, RHSA-2026:33170, RHSA-2026:33226, RHSA-2026:33227, RHSA-2026:33228, RHSA-2026:33229, RHSA-2026:33230, RHSA-2026:33231, RHSA-2026:34211, RHSA-2026:36643, RHSA-2026:37395, RHSA-2026:37396, RLSA-2026:33092, RLSA-2026:33126, RLSA-2026:33226, ROOT-OS-DEBIAN-11-CVE-2026-5450, ROOT-OS-DEBIAN-12-CVE-2026-5450, UBUNTU-CVE-2026-5450, openSUSE-SU-2026:12059-1 ## What is CVE-2026-5450? CVE-2026-5450 is a critical memory corruption vulnerability in Gnu Glibc, published on 20 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Calling the scanf family of functions with a %mc (malloc'd character match) in the GNU C Library version 2.7 to version 2.43 with a format width specifier with an explicit width greater than 1024 could result in a one byte heap buffer overflow. Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow) ## Which versions are affected by CVE-2026-5450? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `glibc` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-all-langpacks` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-benchtests` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-common` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-devel` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-doc` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-gconv-extra` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-aa` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-af` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-agr` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ak` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-am` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-an` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-anp` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ar` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-as` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ast` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ayc` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-az` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-be` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bem` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ber` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bg` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bhb` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bho` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bi` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bn` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bo` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-br` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-brx` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-bs` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-byn` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ca` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ce` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-chr` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-ckb` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-cmn` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-crh` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-cs` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | | `glibc-langpack-csb` | AlmaLinux:10 | All versions | 2.39-126.el10_2.alma.1 | Products: Gnu Glibc. ## How do I fix CVE-2026-5450? Apply the vendor's patch. ## Is CVE-2026-5450 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-5450 exists. ## Other vulnerabilities in Gnu Glibc - [CVE-2023-25139](https://insights.sbomify.com/CVE-2023-25139/): Memory corruption in n/a (critical 9.8) - [CVE-1999-0199](https://insights.sbomify.com/CVE-1999-0199/): Other in n/a (critical 9.8) - [CVE-2019-1010022](https://insights.sbomify.com/CVE-2019-1010022/): Security feature bypass in glibc (critical 9.8) - [CVE-2005-3590](https://insights.sbomify.com/CVE-2005-3590/): Memory corruption in n/a (critical 9.8) - [CVE-2017-18269](https://insights.sbomify.com/CVE-2017-18269/): Memory corruption in n/a (critical 9.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-5450 and fix it if it is affected. What it is: CVE-2026-5450 is a critical memory corruption vulnerability in Gnu Glibc, published on 20 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-5450 exists. Affected product: Gnu Glibc. 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-2026-5450/ (Markdown: https://insights.sbomify.com/CVE-2026-5450/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5450 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5450 - OSV: https://osv.dev/vulnerability/CVE-2026-5450 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-5450/ Summaries are generated and may contain mistakes; the official description above is the record.