Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-3957
Advisory Released Date: 2026-09-28
Advisory Updated Date: 2026-09-28
A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow. (CVE-2026-18355)
A flaw was found in 389 Directory Server. A missing NULL pointer check in the paged results handling of op_shared_search allows an unauthenticated remote attacker to crash the LDAP server by sending a crafted sequence of search requests using the USE_ONE_BACKEND control, resulting in denial of service. (CVE-2026-18453)
Affected Packages:
389-ds-base
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 389-ds-base or yum update --advisory ALAS2-2026-3957 to update your system.
aarch64:
389-ds-base-1.3.10.2-17.amzn2.0.12.aarch64
389-ds-base-libs-1.3.10.2-17.amzn2.0.12.aarch64
389-ds-base-devel-1.3.10.2-17.amzn2.0.12.aarch64
389-ds-base-snmp-1.3.10.2-17.amzn2.0.12.aarch64
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12.aarch64
i686:
389-ds-base-1.3.10.2-17.amzn2.0.12.i686
389-ds-base-libs-1.3.10.2-17.amzn2.0.12.i686
389-ds-base-devel-1.3.10.2-17.amzn2.0.12.i686
389-ds-base-snmp-1.3.10.2-17.amzn2.0.12.i686
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12.i686
src:
389-ds-base-1.3.10.2-17.amzn2.0.12.src
x86_64:
389-ds-base-1.3.10.2-17.amzn2.0.12.x86_64
389-ds-base-libs-1.3.10.2-17.amzn2.0.12.x86_64
389-ds-base-devel-1.3.10.2-17.amzn2.0.12.x86_64
389-ds-base-snmp-1.3.10.2-17.amzn2.0.12.x86_64
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12.x86_64