CVE-2026-18355

Fixed in a distro release EPSS <1%CVSS 7.5

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.

Published 2026-09-07 · CVE record · OSV

Products: Red Hat Directory Server 11.5 E4S for RHEL 8, Red Hat Directory Server 11.7 E4S for RHEL 8, Red Hat Directory Server 11.9 for RHEL 8, Red Hat Directory Server 12.2 E4S for RHEL 9, Red Hat Directory Server 12.4 E4S for RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On, Red Hat Enterprise Linux 8.8 Telecommunications Update Service, Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.6 Extended Update Support, Red Hat Directory Server 13.2, Red Hat Directory Server 12, Red Hat Directory Server 13, Red Hat Enterprise Linux 6

Distro releases