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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat Hardened Images | — | — |
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
| Red Hat | Red Hat OpenShift AI (RHOAI) | — | — |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 5 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | krb5 | 1.22.1-3 | — |
| Debian 13 | krb5 | No fix yet | — |
| Debian 12 | krb5 | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | krb5 | 1.22.1-2ubuntu4.1 | USN-8585-1 |
| Ubuntu 25.10 | krb5 | No fix yet | — |
| Ubuntu 24.04 LTS | krb5 | 1.20.1-6ubuntu2.7 | USN-8585-1 |
| Ubuntu 22.04 LTS | krb5 | 1.19.2-2ubuntu0.8 | USN-8585-1 |
| Ubuntu 20.04 LTS | krb5 | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | krb5 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | krb5 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | krb5 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | krb5 +9 | 1.22.2-8.hum1 | RHSA-2026:25520 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | krb5 | 1.20.1-150600.11.19.1 | SUSE-SU-2026:2848-1 |
| SLES 15 SP6 | krb5 | 1.20.1-150600.11.19.1 | SUSE-SU-2026:2848-1 |
| SLES 15 SP5 | krb5 | 1.20.1-150500.3.23.1 | SUSE-SU-2026:2847-1 |
| SLES 15 SP4 | krb5 | 1.19.2-150400.3.24.1 | SUSE-SU-2026:2954-1 |
| SLES 12 SP5 | krb5 | 1.16.3-46.24.1 | SUSE-SU-2026:2849-1 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP6 | krb5 | 1.20.1-150600.11.19.1 | SUSE-SU-2026:2848-1 |
| SLES for SAP 15 SP5 | krb5 | 1.20.1-150500.3.23.1 | SUSE-SU-2026:2847-1 |
| SLES for SAP 15 SP4 | krb5 | 1.19.2-150400.3.24.1 | SUSE-SU-2026:2954-1 |
| SLE Micro 6.1 | krb5 | 1.21.3-slfo.1.1_5.1 | SUSE-SU-2026:22450-1 |
| SLE Micro 6.0 | krb5 | 1.20.1-9.1 | SUSE-SU-2026:22702-1 |
| SLE Micro 5.5 | krb5 | 1.20.1-150500.3.23.1 | SUSE-SU-2026:2847-1 |
| SLE Micro 5.4 | krb5 | 1.19.2-150400.3.24.1 | SUSE-SU-2026:2954-1 |
| SLE Micro 5.3 | krb5 | 1.19.2-150400.3.24.1 | SUSE-SU-2026:2954-1 |
| SLE HPC 15 SP5 | krb5 | 1.20.1-150500.3.23.1 | SUSE-SU-2026:2847-1 |
| SLE HPC 15 SP4 | krb5 | 1.19.2-150400.3.24.1 | SUSE-SU-2026:2954-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | krb5 | 1.22.2-4.1 | openSUSE-SU-2026:11177-1 |
| openSUSE Leap 16.0 | krb5 | 1.21.3-160000.4.1 | openSUSE-SU-2026:21238-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | libkadm5 +6 | 1.21.3-8.amzn2023.0.1 | ALAS2023-2026-1939 |
| Amazon Linux 2 | libkadm5 +6 | 1.15.1-55.amzn2.2.10 | ALAS2-2026-3798 |
Advisories 13
- WID-SEC-2026-1900 MIT Kerberos: Schwachstelle ermöglicht nicht spezifizierten Angriff BSI CERT-Bund (WID) · Oct 27, 2026
- RHSA-2026:25520 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 6, 2026
- SUSE-SU-2026:22702-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 23, 2026
- USN-8585-1 krb5 vulnerabilities Ubuntu Security Notices (USN) · Jul 22, 2026
- ALAS2-2026-3798 Moderate: krb5 security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jul 20, 2026
- ALAS2023-2026-1939 Moderate: krb5 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Jul 20, 2026
- SUSE-SU-2026:2954-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 15, 2026
- SUSE-SU-2026:2849-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 11, 2026
- SUSE-SU-2026:2847-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 11, 2026
- SUSE-SU-2026:2848-1 Security update for krb5, krb5-mini SUSE / openSUSE Security Updates · Jul 11, 2026
- openSUSE-SU-2026:21238-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 9, 2026
- SUSE-SU-2026:22450-1 Security update for krb5 SUSE / openSUSE Security Updates · Jul 4, 2026
- openSUSE-SU-2026:11177-1 krb5-1.22.2-4.1 on GA media SUSE / openSUSE Security Updates · Jul 3, 2026
References
- RHSA-2026:25520 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-11850 vdb-entry
- RHBZ#2459970 issue-tracking