Is CVE-2026-40355 in the CISA KEV catalog?

No. CVE-2026-40355 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40355?

CVE-2026-40355 has a CVSS v3 base score of 5.9 (Moderate).

What is the EPSS score for CVE-2026-40355?

CVE-2026-40355 has an EPSS score of 0.46% (37th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40355?

Upgrade krb5 on debian 11 to 1.18.3-6+deb11u8 or later. Fixes are available for 51 affected products.

CVE & CISA-KEV Catalog

CVE-2026-40355

MEDIUM

5.9

CVSS v3

NVD

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.

CWE-476NULL Pointer Dereference

How to fix

Remediation Available

krb5Debian

Fixed in:1.18.3-6+deb11u8CVE-2026-40355

Fixed in:1.20.1-2+deb12u5CVE-2026-40355

Fixed in:1.21.3-5+deb13u1CVE-2026-40355

Fixed in:1.22.1-2.1CVE-2026-40355

krb5Red Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:main@aarch64RHSA-2026:12220

Fixed in:main@srcRHSA-2026:12220

Fixed in:main@x86_64RHSA-2026:12220

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5Rocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:main@x86_64RHSA-2026:12220

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:main@srcRHSA-2026:12220

Fixed in:main@aarch64RHSA-2026:12220

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-debugsourceRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-debugsourceRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-develRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-develRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-devel-debuginfoRocky

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

krb5-devel-debuginfoRed Hat / RHEL

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

krb5-libsRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-libsRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-libs-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-libs-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-pkinitRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-pkinitRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-pkinit-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-pkinit-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-serverRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-serverRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-ldapRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-ldapRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-ldap-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-server-ldap-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-workstationRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-workstationRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-workstation-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-workstation-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-xrealmauthzRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-xrealmauthzRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-xrealmauthz-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

krb5-xrealmauthz-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

libkadm5Red Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

libkadm5Rocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

libkadm5-debuginfoRocky

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

libkadm5-debuginfoRed Hat / RHEL

Fixed in:0:1.21.3-10.el10_2RHSA-2026:19145

Fixed in:0:1.18.2-34.el8_10RHSA-2026:16799

Fixed in:0:1.21.1-10.el9_8RHSA-2026:19357

registry.redhat.io/discovery/discoveryRocky

Fixed in:server-rhel9@sha256:6a26bc89c61e7fad594399ceda8e170d66fa241d818eada7a12d9fec6bb08ecc_amd64RHSA-2026:29197

Fixed in:ui-rhel9@sha256:335f5d49155804969d193c3104fd144d7e499e2d5433965b217f379cbcf1cc75_arm64RHSA-2026:29197

Fixed in:server-rhel9@sha256:ccd969d2710875e82896556e7b3c02e39147d03612452af6b0a916b656ce5b34_arm64RHSA-2026:29197

Fixed in:ui-rhel9@sha256:16b33ed961e598805d155db8fea7bb293fb8ef95ddd45169c61fbeb5a8944b6b_amd64RHSA-2026:29197

registry.redhat.io/discovery/discoveryRed Hat / RHEL

Fixed in:ui-rhel9@sha256:335f5d49155804969d193c3104fd144d7e499e2d5433965b217f379cbcf1cc75_arm64RHSA-2026:29197

Fixed in:server-rhel9@sha256:ccd969d2710875e82896556e7b3c02e39147d03612452af6b0a916b656ce5b34_arm64RHSA-2026:29197

Fixed in:ui-rhel9@sha256:16b33ed961e598805d155db8fea7bb293fb8ef95ddd45169c61fbeb5a8944b6b_amd64RHSA-2026:29197

Fixed in:server-rhel9@sha256:6a26bc89c61e7fad594399ceda8e170d66fa241d818eada7a12d9fec6bb08ecc_amd64RHSA-2026:29197

registry.redhat.io/insights-proxy/insights-proxyRocky

Fixed in:container-rhel9@sha256:35a26e08219c8608fd6be94ab0e16947c6d8dd68752b7c7747b65f23f1679492_amd64RHSA-2026:22634

Fixed in:container-rhel9@sha256:97b534defdc32202c8208b1ab1411a1e1085accaa79372437d467968fae0ba53_arm64RHSA-2026:22634

registry.redhat.io/insights-proxy/insights-proxyRed Hat / RHEL

Fixed in:container-rhel9@sha256:35a26e08219c8608fd6be94ab0e16947c6d8dd68752b7c7747b65f23f1679492_amd64RHSA-2026:22634

Fixed in:container-rhel9@sha256:97b534defdc32202c8208b1ab1411a1e1085accaa79372437d467968fae0ba53_arm64RHSA-2026:22634

registry.redhat.io/rhui5/cdsRocky

Fixed in:rhel9@sha256:29229a9b1908d9586aa60ae96ea4cab29316c058665ea4e10bd7d88e3434f38a_amd64RHSA-2026:21275

registry.redhat.io/rhui5/cdsRed Hat / RHEL

Fixed in:rhel9@sha256:29229a9b1908d9586aa60ae96ea4cab29316c058665ea4e10bd7d88e3434f38a_amd64RHSA-2026:21275

registry.redhat.io/rhui5/haproxyRed Hat / RHEL

Fixed in:rhel9@sha256:eeceb83a297bdb2778a63fa0e55d441ba316b77be786280746348fdcdeae866d_amd64RHSA-2026:21275

registry.redhat.io/rhui5/haproxyRocky

Fixed in:rhel9@sha256:eeceb83a297bdb2778a63fa0e55d441ba316b77be786280746348fdcdeae866d_amd64RHSA-2026:21275

registry.redhat.io/rhui5/installerRed Hat / RHEL

Fixed in:rhel9@sha256:fb8d5c681efa515095f164334fde48bb2c4160069ba7512ddbf16a865c65ae17_amd64RHSA-2026:21275

registry.redhat.io/rhui5/installerRocky

Fixed in:rhel9@sha256:fb8d5c681efa515095f164334fde48bb2c4160069ba7512ddbf16a865c65ae17_amd64RHSA-2026:21275

registry.redhat.io/rhui5/rhuaRed Hat / RHEL

Fixed in:rhel9@sha256:ae3724c290b6e0c536cadae4dbe38fc1241fb88520db381e04bfbd1e489989e8_amd64RHSA-2026:21275

registry.redhat.io/rhui5/rhuaRocky

Fixed in:rhel9@sha256:ae3724c290b6e0c536cadae4dbe38fc1241fb88520db381e04bfbd1e489989e8_amd64RHSA-2026:21275

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U

Exploit Intelligence

0.46%probability of exploitation in 30 days

37thpercentile

Low risk: more likely to be exploited than 37% of all known CVEs.

References

Other references3

Related Vulnerabilities

Other CWE-476 (NULL Pointer Dereference) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-21758	High	7.5	92%	-	Fix
CVE-2023-21547	High	7.5	88%	-	Fix
CVE-2014-3470	Medium	4.3	86%	-	Fix
CVE-2021-44224	High	8.2	82%	-	Fix
CVE-2016-0742	High	7.5	82%	-	Fix
CVE-2009-1386	Medium	5.0	80%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-28.