Amazon Linux 2 Security Advisory: ALAS2-2026-3798
Advisory Released Date: 2026-07-20
Advisory Updated Date: 2026-07-20
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. (CVE-2026-11850)
Affected Packages:
krb5
Note:
This advisory is applicable to Amazon Linux 2 (AL2) Core repository. Visit this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update krb5 or yum update --advisory ALAS2-2026-3798 to update your system.
aarch64:
krb5-devel-1.15.1-55.amzn2.2.10.aarch64
krb5-libs-1.15.1-55.amzn2.2.10.aarch64
krb5-server-1.15.1-55.amzn2.2.10.aarch64
krb5-server-ldap-1.15.1-55.amzn2.2.10.aarch64
krb5-workstation-1.15.1-55.amzn2.2.10.aarch64
krb5-pkinit-1.15.1-55.amzn2.2.10.aarch64
libkadm5-1.15.1-55.amzn2.2.10.aarch64
krb5-debuginfo-1.15.1-55.amzn2.2.10.aarch64
i686:
krb5-devel-1.15.1-55.amzn2.2.10.i686
krb5-libs-1.15.1-55.amzn2.2.10.i686
krb5-server-1.15.1-55.amzn2.2.10.i686
krb5-server-ldap-1.15.1-55.amzn2.2.10.i686
krb5-workstation-1.15.1-55.amzn2.2.10.i686
krb5-pkinit-1.15.1-55.amzn2.2.10.i686
libkadm5-1.15.1-55.amzn2.2.10.i686
krb5-debuginfo-1.15.1-55.amzn2.2.10.i686
src:
krb5-1.15.1-55.amzn2.2.10.src
x86_64:
krb5-devel-1.15.1-55.amzn2.2.10.x86_64
krb5-libs-1.15.1-55.amzn2.2.10.x86_64
krb5-server-1.15.1-55.amzn2.2.10.x86_64
krb5-server-ldap-1.15.1-55.amzn2.2.10.x86_64
krb5-workstation-1.15.1-55.amzn2.2.10.x86_64
krb5-pkinit-1.15.1-55.amzn2.2.10.x86_64
libkadm5-1.15.1-55.amzn2.2.10.x86_64
krb5-debuginfo-1.15.1-55.amzn2.2.10.x86_64