CVE-2026-40356 Integer overflow in Kerberos 5
Medium 5.9
Published
Updated
Check this codebase for CVE-2026-40356 and fix it if it is affected.
What it is: CVE-2026-40356 is a medium-severity vulnerability in Mit Kerberos 5, published on 28 Apr 2026. 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-2026-40356 in the wild and no public exploit code.
Affected product: Mit Kerberos 5. 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-2026-40356/ (Markdown: https://insights.sbomify.com/CVE-2026-40356/index.md)
An unauthenticated remote attacker can cause a denial of service via integer underflow in MIT Kerberos when NegoEx is registered.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40356?
CVE-2026-40356 is a medium-severity vulnerability in Mit Kerberos 5, published on 28 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process to terminate in parse_message.
Weakness: CWE-191
Which versions are affected by CVE-2026-40356?
It affects 1 product.
Linux distribution packages (40)
krb5-devel Red Hat:rhel_e4s:9.2::appstream | All versions | 0:1.20.1-9.el9_2.6 |
krb5 Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-debugsource Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-libs Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-libs-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-pkinit Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-pkinit-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-server Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-server-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-server-ldap Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-server-ldap-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-workstation Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-workstation-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
libkadm5 Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
libkadm5-debuginfo Red Hat:rhel_e4s:9.2::baseos | All versions | 0:1.20.1-9.el9_2.6 |
krb5-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-debugsource Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-devel Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-libs-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-pkinit-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server-ldap-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5-workstation-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
libkadm5-debuginfo Red Hat:rhel_e4s:9.4::appstream | All versions | 0:1.21.1-2.el9_4.5 |
krb5 Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-debugsource Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-libs Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-libs-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-pkinit Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-pkinit-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server-ldap Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-server-ldap-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-workstation Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
krb5-workstation-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
libkadm5 Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
libkadm5-debuginfo Red Hat:rhel_e4s:9.4::baseos | All versions | 0:1.21.1-2.el9_4.5 |
Products include Mit Kerberos 5.
How do I fix CVE-2026-40356?
Upgrade to a fixed version.
Is CVE-2026-40356 being exploited?
There is no known exploitation of CVE-2026-40356 in the wild and no public exploit code.
Other vulnerabilities in Mit Kerberos 5
Sources
Also known as AZL-85238, BELL-CVE-2026-40356, DEBIAN-CVE-2026-40356, ECHO-874c-29e0-d62b, GHSA-f7p3-6rhj-p7jv, JLSEC-2026-1259 and 4 more.