CVE-2026-11850

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

Published Jun 11, 2026 CVSS 3.1 · 5 Medium EPSS < 1% KEV · Not listed
Description
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

Vendor 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.

Tracking

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Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-8585-1 Kerberos vulnerabilities
History
Type Values Removed Values Added
First Time appeared Redhat openshift Ai
CPEs cpe:/a:redhat:openshift_ai
Vendors & Products Redhat openshift Ai
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:10
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
CPEs cpe:/a:redhat:openshift:5
Type Values Removed Values Added
First Time appeared Redhat hardened Images
Redhat openshift Container Platform
Vendors & Products Redhat hardened Images
Redhat openshift Container Platform
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Krb5: krb5: integer underflow in berval2tl_data() leads to heap out-of-bounds read
First Time appeared Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
Weaknesses CWE-191
CPEs cpe:/a:redhat:hummingbird:1
cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
References
Metrics cvssV3_1

{'score': 5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 7, 2026, 5:01 AM
Reserved
Jun 10, 2026, 8:12 AM
Status
Awaiting Analysis
Published
Jun 11, 2026, 10:16 AM
Modified
Nov 6, 2026, 8:17 AM
Severity
Moderate
Public date
Jun 10, 2026, 12:00 AM