Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-4003
Advisory Released Date: 2026-10-24
Advisory Updated Date: 2026-10-26
A flaw was found in 389-ds-base. An unauthenticated remote attacker can send a complete LDAP operation followed by the first bytes of an incomplete LDAPMessage on the same connection, causing the server to hand that connection to a second worker thread before the first worker's result is flushed. The second worker blocks until nsslapd-ioblocktimeout while holding the connection mutex, preventing delivery of the completed operation's result. Repeating this across a small number of connections proportional to the configured worker-thread pool size exhausts the entire pool under default configuration, denying service to all clients (anonymous and authenticated, plaintext and TLS) for as long as the attacker maintains the connections. (CVE-2026-86344)
A flaw was found in 389-ds-base. The server does not discard plaintext bytes already buffered from a client connection when negotiating StartTLS, allowing an on-path attacker to inject a crafted LDAP message that is processed after the TLS upgrade and whose response is delivered to the client in place of the client's own pending operation's response, due to messageID collision. This can cause a client application to treat a failed authentication (bind) attempt as successful. (CVE-2026-86345)
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 ALAS2-2026-4003 to update your system.
aarch64:
389-ds-base-1.3.10.2-17.amzn2.0.14.aarch64
389-ds-base-libs-1.3.10.2-17.amzn2.0.14.aarch64
389-ds-base-devel-1.3.10.2-17.amzn2.0.14.aarch64
389-ds-base-snmp-1.3.10.2-17.amzn2.0.14.aarch64
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.14.aarch64
i686:
389-ds-base-1.3.10.2-17.amzn2.0.14.i686
389-ds-base-libs-1.3.10.2-17.amzn2.0.14.i686
389-ds-base-devel-1.3.10.2-17.amzn2.0.14.i686
389-ds-base-snmp-1.3.10.2-17.amzn2.0.14.i686
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.14.i686
src:
389-ds-base-1.3.10.2-17.amzn2.0.14.src
x86_64:
389-ds-base-1.3.10.2-17.amzn2.0.14.x86_64
389-ds-base-libs-1.3.10.2-17.amzn2.0.14.x86_64
389-ds-base-devel-1.3.10.2-17.amzn2.0.14.x86_64
389-ds-base-snmp-1.3.10.2-17.amzn2.0.14.x86_64
389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.14.x86_64