How severe is CVE-2026-40355?

CVE-2026-40355 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-2026-40355 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-2026-40355?

CVE-2026-40355 affects Mit Kerberos 5. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40355?

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

Does CVE-2026-40355 have an EU (EUVD) identifier?

Yes. CVE-2026-40355 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25981.

When was CVE-2026-40355 published?

CVE-2026-40355 was published on 2026-04-28 and last updated on 2026-07-08.

CVE-2026-40355

CVE-2026-40355 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-476.

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-2026-25981
Weakness: CWE-476
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 a NULL pointer dereference 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, causing the process to terminate in parse_nego_message.

Frequently asked questions

What is CVE-2026-40355?: In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference 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, causing the process to terminate in parse_nego_message.
How severe is CVE-2026-40355?: CVE-2026-40355 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-2026-40355 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-2026-40355?: CVE-2026-40355 affects Mit Kerberos 5. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40355?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40355 have an EU (EUVD) identifier?: Yes. CVE-2026-40355 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25981.
When was CVE-2026-40355 published?: CVE-2026-40355 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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