# CVE-2026-18355: 389-ds-base: A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base)

CVE-2026-18355 is fixed in 15 products on 1 platform, first by FEDORA-2026-0B8BC362B1, released September 7, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-18355
- Priority: High
- CVSS: 9.8 (important)
- EPSS: 0.0084
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 7, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | 389-ds opensuse-leap 16.0 | 3.0.7~git2.2846d5288-160000.1.1 | [OPENSUSE-SU-2026:21950-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21950-1.md) | Sep 24, 2026 |
| Linux | 389-ds sles 15.6 | 2.2.11~git12.1e612cde2-150600.8.38.1 | [SUSE-SU-2026:4929-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4929-1.md) | Nov 7, 2026 |
| Linux | 389-ds sles 15.7 | 2.8.2~git10.030ada7a6-150700.3.25.1 | [SUSE-SU-2026:4380-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4380-1.md) | Sep 28, 2026 |
| Linux | 389-ds sles 16.0 | 3.0.7~git2.2846d5288-160000.1.1 | [SUSE-SU-2026:23916-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23916-1.md) | Sep 24, 2026 |
| Linux | 389-ds-base Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base RHEL 10 | 3.0.6-21.el10_0 | [RHSA-2026:64804](https://patchblox.com/security/data/fix/linux/rhsa-2026-64804.md) | Sep 10, 2026 |
| Linux | 389-ds-base RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | 389-ds-base RHEL 9 | 0:2.8.0-10.el9_8 | [RHSA-2026:64784](https://patchblox.com/security/data/fix/linux/rhsa-2026-64784.md) | Sep 13, 2026 |
| Linux | 389-ds-base almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | 389-ds-base almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | 389-ds-base almalinux 9 | 2.8.0-10.el9_8 | [ALSA-2026:64784](https://patchblox.com/security/data/fix/linux/alsa-2026-64784.md) | Sep 8, 2026 |
| Linux | 389-ds-base ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | 389-ds-base ol 9 | 0:2.8.0-10.el9_8 | [ELSA-2026-64784-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64784-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base rocky 10 | 0:3.2.0-10.el10_2 | [RLSA-2026:64785](https://patchblox.com/security/data/fix/linux/rlsa-2026-64785.md) | Sep 9, 2026 |
| Linux | 389-ds-base rocky 8 | 0:1.4.3.39-28.module+el8.10.0+40311+cd962df1 | [RLSA-2026:64791](https://patchblox.com/security/data/fix/linux/rlsa-2026-64791.md) | Sep 9, 2026 |
| Linux | 389-ds-base rocky 9 | 0:2.8.0-10.el9_8 | [RLSA-2026:64784](https://patchblox.com/security/data/fix/linux/rlsa-2026-64784.md) | Sep 9, 2026 |
| Linux | 389-ds-base-bdb almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | 389-ds-base-bdb ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-debuginfo Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-debugsource Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-devel Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-devel RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | 389-ds-base-devel RHEL 9 | 0:2.8.0-10.el9_8 | [RHSA-2026:64784](https://patchblox.com/security/data/fix/linux/rhsa-2026-64784.md) | Sep 13, 2026 |
| Linux | 389-ds-base-devel almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | 389-ds-base-devel almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | 389-ds-base-devel almalinux 9 | 2.8.0-10.el9_8 | [ALSA-2026:64784](https://patchblox.com/security/data/fix/linux/alsa-2026-64784.md) | Sep 8, 2026 |
| Linux | 389-ds-base-devel ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-devel ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | 389-ds-base-devel ol 9 | 0:2.8.0-10.el9_8 | [ELSA-2026-64784-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64784-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-legacy-tools RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | 389-ds-base-legacy-tools almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | 389-ds-base-legacy-tools ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | 389-ds-base-libs Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-libs RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | 389-ds-base-libs RHEL 9 | 0:2.8.0-10.el9_8 | [RHSA-2026:64784](https://patchblox.com/security/data/fix/linux/rhsa-2026-64784.md) | Sep 13, 2026 |
| Linux | 389-ds-base-libs almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | 389-ds-base-libs almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | 389-ds-base-libs almalinux 9 | 2.8.0-10.el9_8 | [ALSA-2026:64784](https://patchblox.com/security/data/fix/linux/alsa-2026-64784.md) | Sep 8, 2026 |
| Linux | 389-ds-base-libs ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-libs ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | 389-ds-base-libs ol 9 | 0:2.8.0-10.el9_8 | [ELSA-2026-64784-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64784-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-libs-debuginfo Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-robdb-libs Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-robdb-libs-debuginfo Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-snmp Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | 389-ds-base-snmp RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | 389-ds-base-snmp RHEL 9 | 0:2.8.0-10.el9_8 | [RHSA-2026:64784](https://patchblox.com/security/data/fix/linux/rhsa-2026-64784.md) | Sep 13, 2026 |
| Linux | 389-ds-base-snmp almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | 389-ds-base-snmp almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | 389-ds-base-snmp almalinux 9 | 2.8.0-10.el9_8 | [ALSA-2026:64784](https://patchblox.com/security/data/fix/linux/alsa-2026-64784.md) | Sep 8, 2026 |
| Linux | 389-ds-base-snmp ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-snmp ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | 389-ds-base-snmp ol 9 | 0:2.8.0-10.el9_8 | [ELSA-2026-64784-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64784-0.md) | Sep 8, 2026 |
| Linux | 389-ds-base-snmp-debuginfo Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | cockpit-389-ds Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | python3-lib389 Fedora 43 | 3.1.5-4.fc43 | [FEDORA-2026-0B8BC362B1](https://patchblox.com/security/data/fix/linux/fedora-2026-0b8bc362b1.md) | Sep 7, 2026 |
| Linux | python3-lib389 RHEL 8 | 0:1.4.3.39-28.module+el8.10.0+24822+205d20dc | [RHSA-2026:64791](https://patchblox.com/security/data/fix/linux/rhsa-2026-64791.md) | Sep 13, 2026 |
| Linux | python3-lib389 RHEL 9 | 0:2.8.0-10.el9_8 | [RHSA-2026:64784](https://patchblox.com/security/data/fix/linux/rhsa-2026-64784.md) | Sep 13, 2026 |
| Linux | python3-lib389 almalinux 10 | 3.2.0-10.el10_2 | [ALSA-2026:64785](https://patchblox.com/security/data/fix/linux/alsa-2026-64785.md) | Sep 8, 2026 |
| Linux | python3-lib389 almalinux 8 | 1.4.3.39-28.module_el8.10.0+4274+00f9a3f1 | [ALSA-2026:64791](https://patchblox.com/security/data/fix/linux/alsa-2026-64791.md) | Sep 8, 2026 |
| Linux | python3-lib389 almalinux 9 | 2.8.0-10.el9_8 | [ALSA-2026:64784](https://patchblox.com/security/data/fix/linux/alsa-2026-64784.md) | Sep 8, 2026 |
| Linux | python3-lib389 ol 10 | 0:3.2.0-10.el10_2 | [ELSA-2026-64785-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64785-0.md) | Sep 8, 2026 |
| Linux | python3-lib389 ol 8 | 0:1.4.3.39-28.module+el8.10.0+91024+7bf29691 | [ELSA-2026-64791-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64791-0.md) | Sep 10, 2026 |
| Linux | python3-lib389 ol 9 | 0:2.8.0-10.el9_8 | [ELSA-2026-64784-0](https://patchblox.com/security/data/fix/linux/elsa-2026-64784-0.md) | Sep 8, 2026 |

---

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