CVE-2026-5450 scanf %mc off-by-one heap buffer overflow
Critical 9.8
Published
Updated
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)
A heap buffer overflow in glibc's scanf function allows attackers to execute arbitrary code or cause denial of service via crafted input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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.
Which versions are affected by CVE-2026-5450?
It affects 1 product.
Linux distribution packages (40)
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 include Gnu Glibc.
How do I fix CVE-2026-5450?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
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
Sources
Also known as ALSA-2026:33092, ALSA-2026:33126, ALSA-2026:33226, AZL-83093, CLSA-2026-1782488061, DEBIAN-CVE-2026-5450 and 25 more.