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Vulnerability · Published Sep 7, 2026 · Assigned by redhat

CVE-2026-18355389-ds-base: 389-ds-base: heap buffer overflow via sasl wrapped-record length lower-bound underflow in sasl_io_start_packet()

High 7.5

In plain English

A high-severity security flaw in Red Hat Directory Server 11.5 E4S for RHEL 8 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 58% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.8%top 42.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10389-ds-base3.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:8389-ds-base1.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:9389-ds-base2.8.0-10.el9_8ALSA-2026:64784
AlmaLinux:10389-ds-base-bdb3.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:10389-ds-base-devel3.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:8389-ds-base-devel1.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:9389-ds-base-devel2.8.0-10.el9_8ALSA-2026:64784
AlmaLinux:8389-ds-base-legacy-tools1.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:10389-ds-base-libs3.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:8389-ds-base-libs1.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:9389-ds-base-libs2.8.0-10.el9_8ALSA-2026:64784
AlmaLinux:10389-ds-base-snmp3.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:8389-ds-base-snmp1.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:9389-ds-base-snmp2.8.0-10.el9_8ALSA-2026:64784
AlmaLinux:10python3-lib3893.2.0-10.el10_2ALSA-2026:64785
AlmaLinux:8python3-lib3891.4.3.39-28.module_el8.10.0+4274+00f9a3f1ALSA-2026:64791
AlmaLinux:9python3-lib3892.8.0-10.el9_8ALSA-2026:64784
Debian:12389-ds-baseno fix listedDEBIAN-CVE-2026-18355
Debian:13389-ds-baseno fix listedDEBIAN-CVE-2026-18355
Rocky Linux:10389-ds-base0:3.2.0-10.el10_2RLSA-2026:64785
Rocky Linux:8389-ds-base0:1.4.3.39-28.module+el8.10.0+40311+cd962df1RLSA-2026:64791
Rocky Linux:9389-ds-base0:2.8.0-10.el9_8RLSA-2026:64784
Ubuntu:22.04:LTS389-ds-baseno fix listedUBUNTU-CVE-2026-18355
Ubuntu:24.04:LTS389-ds-baseno fix listedUBUNTU-CVE-2026-18355
Ubuntu:26.04:LTS389-ds-baseno fix listedUBUNTU-CVE-2026-18355
Ubuntu:26.10389-ds-baseno fix listedUBUNTU-CVE-2026-18355

Affected products (as reported)

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

Weakness: CWE-191 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

References