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MIT krb5 EUVDEUVD-2026-36219

| CVE-2026-11850 MEDIUM
Integer Underflow (CWE-191)
2026-06-11 redhat GHSA-85rq-mqr4-hjw7
Buffer Overflow Integer Overflow Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Openshift Container Platform 4 Red Hat Hardened Images Red Hat
5.0
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
5.0 MEDIUM
AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H
vuln.today AI
5.0 MEDIUM

AV:N reflects network-based LDAP communication; AC:H and PR:H reflect required control of the LDAP KDB backend; A:H for KDC crash; C:L for heap read leak to an already-privileged attacker.

3.1 AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H
4.0 AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
Red Hat
5.0 MEDIUM
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Network
Attack Complexity
High
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High

Lifecycle Timeline

2
Analysis Generated
Jun 11, 2026 - 10:17 vuln.today
CVE Published
Jun 11, 2026 - 09:49 cve.org
MEDIUM 5.0

DescriptionCVE.org

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.

AnalysisAI

Heap out-of-bounds read in MIT krb5's LDAP KDB plugin allows a compromised or malicious LDAP backend to crash the KDC or kadmind process, or leak heap memory. The flaw exists in berval2tl_data() within libkdb_ldap and is triggered when the LDAP server returns a krbExtraData attribute with bv_len less than 2, causing an unsigned integer underflow that drives a memcpy of up to 65,534 bytes from a near-zero-length source buffer. Exploitation requires prior control of the LDAP KDB backend server (PR:H, AC:H), constraining real-world risk to insider or supply-chain threat scenarios; no public exploit or CISA KEV listing exists at time of analysis.

Technical ContextAI

The vulnerable function berval2tl_data() resides in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c within MIT krb5's optional LDAP KDB (Key Distribution Center Database) plugin. This plugin allows krb5 to store and retrieve Kerberos principal data from an LDAP directory rather than the default file-based BDB/LMDB store. CWE-191 (Integer Underflow) describes the root cause precisely: the expression (bv_len - 2) is performed on an unsigned type without a prior bounds check that bv_len >= 2. When bv_len is 0 or 1, unsigned wraparound occurs and the result is then truncated to uint16_t, yielding 0xFFFE (65534) or 0xFFFF (65535). A malloc of this inflated size succeeds normally, but the ensuing memcpy reads up to 65,534 bytes beyond a 0-1 byte source buffer on the heap, constituting a classic heap buffer over-read. Affected deployments span Red Hat Enterprise Linux 6 through 10, Red Hat Hardened Images, and Red Hat OpenShift Container Platform 4 per CPE strings cpe:2.3:a:red_hat:red_hat_enterprise_linux_*:*:*:*:*:*:*:*:* and cpe:2.3:a:red_hat:red_hat_openshift_container_platform_4:*:*:*:*:*:*:*:*.

RemediationAI

Apply the vendor-supplied patch from Red Hat once released; no exact patched version has been confirmed in the available data at time of analysis. Monitor https://access.redhat.com/security/cve/CVE-2026-11850 and https://bugzilla.redhat.com/show_bug.cgi?id=2459970 for patch release announcements and exact fixed package versions. As an immediate compensating control, restrict the LDAP servers listed in krb5.conf or kdc.conf ldap_servers to known-trusted, hardened hosts and enforce mutual TLS between the KDC/kadmind and LDAP server - this prevents a network MITM from injecting malformed krbExtraData attributes, though it does not protect against a fully compromised LDAP server. The most complete mitigation short of patching is to migrate the Kerberos principal database to the non-LDAP backend (BDB or LMDB), which eliminates libkdb_ldap entirely from the attack surface; note this requires a principal database export and re-import and may affect LDAP-integrated identity workflows. If LDAP KDB is operationally required, apply strict LDAP ACLs to limit which accounts can write the krbExtraData attribute, reducing the blast radius of a compromised LDAP account.

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Same weakness CWE-191 – Integer Underflow

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Affected
SLES15-SP6-CHOST-BYOS Affected
SLES15-SP6-CHOST-BYOS-Aliyun Affected
SLES15-SP6-CHOST-BYOS-Azure Affected
SLES15-SP6-CHOST-BYOS-EC2 Affected

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EUVD-2026-36219 vulnerability details – vuln.today
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