How severe is CVE-2026-40356?

CVE-2026-40356 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-40356 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40356?

CVE-2026-40356 affects Mit Kerberos 5. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40356?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40356 have an EU (EUVD) identifier?

Yes. CVE-2026-40356 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25993.

When was CVE-2026-40356 published?

CVE-2026-40356 was published on 2026-04-28 and last updated on 2026-07-08.

CVE-2026-40356

CVE-2026-40356 is a medium-severity vulnerability in Mit Kerberos 5 with a CVSS 3.x base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-191.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-25993
Weakness: CWE-191
Affected product: Mit Kerberos 5
Published: 2026-04-28
Last modified: 2026-07-08

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.

Frequently asked questions

What is CVE-2026-40356?: 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.
How severe is CVE-2026-40356?: CVE-2026-40356 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-40356 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40356?: CVE-2026-40356 affects Mit Kerberos 5. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40356?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40356 have an EU (EUVD) identifier?: Yes. CVE-2026-40356 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25993.
When was CVE-2026-40356 published?: CVE-2026-40356 was published on 2026-04-28 and last updated on 2026-07-08.

References

Affected products (1)

cpe:2.3:a:mit:kerberos_5:*:*:*:*:*:*:*:*

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