# CVE-2026-11850: Krb5: krb5: integer underflow in berval2tl_data() leads to heap out-of-bounds read

Status: published. Published: 2026-06-11. Updated: 2026-11-06.

An integer underflow vulnerability was found in MIT krb5 in the berval2tl_data() function in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c. The function performs an unsigned subtraction (bv_len - 2) without a prior bounds check. When bv_len is 0 or 1, the subtraction wraps to a large value which is then truncated to uint16_t, yielding 0xFFFE (65534) or 0xFFFF (65535). The subsequent malloc succeeds and memcpy reads up to 65534 bytes from a 0-1 byte buffer, resulting in a heap out-of-bounds read.
The attack vector involves a malicious or compromised LDAP KDB backend returning a krbExtraData attribute with bv_len < 2, triggering the underflow when the KDC or kadmind reads principal data.

## Remediation

- workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Hardened Images (krb5-main): ≥ 1.22.2-8.hum1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (krb5): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (krb5): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (krb5): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (krb5): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (krb5): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-ai-gateway-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-core-bff-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-dashboard-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-dashboard-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-data-science-pipelines-operator-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kf-notebook-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kserve-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kserve-llmisvc-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kserve-module-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kuberay-operator-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-kube-rbac-proxy-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-llama-stack-k8s-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-maas-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mlflow-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mlflow-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-agent-ops-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-automl-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-autorag-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-eval-hub-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-gen-ai-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-maas-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-mlflow-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-mod-arch-model-registry-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-model-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-model-registry-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-model-serving-api-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-notebook-controller-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-ogx-k8s-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-ogx-module-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-training-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-trustyai-service-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift AI (RHOAI) (rhoai/odh-workbenches-operator-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 5 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H; source: CNA: redhat

- CVSS 3.1: 5 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.27% as of 2026-11-05; percentile 19.42%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-191

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:25520 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-11850 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2459970 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:25520 (secalert@redhat.com)

- https://access.redhat.com/security/cve/CVE-2026-11850 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2459970 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-11850; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11850; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-11850; retrieved 2026-11-05; source updated Not reported

Revision: 3e63886bec8ab451ba8d1c33cb6f0b3302b13954c8ff6d62943cb4405ce04889

Canonical: https://y2.dev/cve/CVE-2026-11850

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