--- id: CVE-2026-40356 title: >- 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 summary: >- 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 unauthenticat… severity: medium cvss: 5.9 cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H' cwe: - CWE-191 vendor: mit product: kerberos_5 affected: - 'kerberos_5 >= 1.18.0, <= 1.22.2' published: '2026-04-28' updated: '2026-07-08' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40356' references: - url: >- https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html label: cve@mitre.org - url: >- https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f label: cve@mitre.org - url: 'https://web.mit.edu/kerberos/advisories/' label: cve@mitre.org - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40356.json - url: 'https://access.redhat.com/security/cve/CVE-2026-40356' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2463368' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-40356' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40356' - url: 'https://access.redhat.com/errata/RHSA-2026:19145' - url: 'https://access.redhat.com/errata/RHSA-2026:24685' - url: 'https://access.redhat.com/errata/RHSA-2026:24686' - url: 'https://access.redhat.com/errata/RHSA-2026:24683' - url: 'https://access.redhat.com/errata/RHSA-2026:19357' - url: 'https://access.redhat.com/errata/RHSA-2026:16799' - url: 'https://access.redhat.com/errata/RHSA-2026:72502' - url: 'https://access.redhat.com/errata/RHSA-2026:43692' - url: 'https://access.redhat.com/errata/RHSA-2026:29197' - url: 'https://access.redhat.com/errata/RHSA-2026:12220' - url: 'https://access.redhat.com/errata/RHSA-2026:22634' - url: 'https://access.redhat.com/errata/RHSA-2026:58981' - url: 'https://access.redhat.com/errata/RHSA-2026:21275' - url: 'https://access.redhat.com/errata/RHSA-2026:74674' - url: 'https://access.redhat.com/errata/RHSA-2026:82322' - url: 'https://access.redhat.com/errata/RHSA-2026:82304' - url: 'https://access.redhat.com/errata/RHSA-2026:82354' - url: 'https://access.redhat.com/errata/RHSA-2026:82372' - url: 'https://access.redhat.com/errata/RHSA-2026:82347' tags: - nvd - csaf - vex - red-hat epss: 0.00604 epssPercentile: 0.48682 ingestedAt: '2026-07-08T12:51:00.671Z' patched: - enterprise_linux_appstream_v_10 - enterprise_linux_appstream_e4s_v_9_2 - enterprise_linux_appstream_e4s_v_9_4 - enterprise_linux_appstream_eus_v_9_6 - enterprise_linux_appstream_v_9 - enterprise_linux_baseos_v_10 - enterprise_linux_baseos_v_8 - enterprise_linux_baseos_e4s_v_9_2 - enterprise_linux_baseos_e4s_v_9_4 - enterprise_linux_baseos_eus_v_9_6 - enterprise_linux_baseos_v_9 - cert_manager_support_for_red_hat_openshift_release 1.20 - openshift_api_for_data_protection 1.6 - discovery 2 - hardened_images - insights_proxy 1.5 - update_infrastructure 5 --- ## Overview 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. ## Affected - `kerberos_5 >= 1.18.0, <= 1.22.2` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **RHSA-2026:19145** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-05-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:19145) - **RHSA-2026:24685** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2) · released 2026-06-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:24685) - **RHSA-2026:24686** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4) · released 2026-06-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:24686) - **RHSA-2026:24683** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6) · released 2026-06-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:24683) - **RHSA-2026:19357** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-05-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:19357) - **RHSA-2026:16799** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-05-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:16799) - **RHSA-2026:72502** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.20 · released 2026-09-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:72502) - **RHSA-2026:43692** · Red Hat · fixed in: OpenShift API for Data Protection 1.6 · released 2026-07-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:43692) - **RHSA-2026:29197** · Red Hat · fixed in: Red Hat Discovery 2 · released 2026-06-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:29197) - **RHSA-2026:12220** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-04-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:12220) - **RHSA-2026:22634** · Red Hat · fixed in: Red Hat Insights proxy 1.5 · released 2026-06-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:22634) - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · updated 2026-10-14 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40356.json) - **RHSA-2026:82322** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.17 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82322) - **RHSA-2026:82304** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.17 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82304) - **RHSA-2026:82354** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.18 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82354) - **RHSA-2026:82372** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.18 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82372) - **RHSA-2026:82347** · Red Hat · fixed in: Cert Manager support for Red Hat OpenShift release 1.18 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82347)