--- id: CVE-2026-18355 title: >- A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base) summary: >- 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, … severity: high cvss: 7.5 cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-191 vendor: Red Hat product: 'redhat-ds:11' affected: - 'redhat-ds:11 (all versions)' - 'redhat-ds:11 (all versions)' - 'redhat-ds:12 (all versions)' - 'redhat-ds:12 (all versions)' - 389-ds-base (all versions) - 389-ds-base (all versions) - 389-ds-base (all versions) - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - '389-ds:1.4 (all versions)' - 389-ds-base (all versions) - 389-ds-base (all versions) - 389-ds-base (all versions) - 389-ds-base (all versions) - dirsrv/dirsrv-container-rhel10 (all versions) - 'redhat-ds:12/389-ds-base (all versions)' - 389-ds-base - 389-ds-base published: '2026-09-07' updated: '2026-09-08' sourceUpdated: '2026-09-08T22:17:40.127' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18355' references: - url: 'https://access.redhat.com/errata/RHSA-2026:64771' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64776' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64778' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64779' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64780' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64781' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64783' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64784' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64785' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64789' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64790' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64791' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64792' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64793' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:64804' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:65119' label: secalert@redhat.com - url: 'https://access.redhat.com/security/cve/CVE-2026-18355' label: secalert@redhat.com - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2509186' label: secalert@redhat.com - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-18355.json - url: 'https://www.cve.org/CVERecord?id=CVE-2026-18355' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18355' tags: - nvd - cve.org - csaf - vex - red-hat ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-09-08T16:40:59.242163Z' epss: 0.00837 epssPercentile: 0.56259 ingestedAt: '2026-09-08T17:06:31.887Z' patched: - enterprise_linux_server_v_7_els - enterprise_linux_server_optional_v_7_els - directory_server_11_9_for_rhel 8 - enterprise_linux_appstream_eus_v_10_0 - enterprise_linux_appstream_v_10 - enterprise_linux_appstream_v_8 - enterprise_linux_appstream_aus_v_8_4 - enterprise_linux_appstream_eus_extension_v_8_4 - enterprise_linux_appstream_aus_v_8_6 - enterprise_linux_appstream_eus_extension_v_8_6 - enterprise_linux_appstream_e4s_v_8_8 - enterprise_linux_appstream_tus_v_8_8 - enterprise_linux_appstream_e4s_v_9_2 - enterprise_linux_appstream_e4s_v_9_4 - enterprise_linux_appstream_eus_v_9_6 - enterprise_linux_appstream_v_9 - directory_server_11_7_e4s_for_rhel 8 - directory_server_12_2_e4s_for_rhel 9 - directory_server_12_4_e4s_for_rhel 9 - enterprise_linux_codeready_linux_builder_eus_v_10_0 - enterprise_linux_codeready_linux_builder_v_10 - codeready_linux_builder_eus_v_9_6 - enterprise_linux_codeready_linux_builder_v_9 - directory_server 13.2 --- ## Overview 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. ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **RHSA-2026:64771** · Red Hat · fixed in: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64771) - **RHSA-2026:64793** · Red Hat · fixed in: Red Hat Directory Server 11.9 for RHEL 8 · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64793) - **RHSA-2026:64804** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64804) - **RHSA-2026:64785** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64785) - **RHSA-2026:64791** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64791) - **RHSA-2026:64789** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64789) - **RHSA-2026:64790** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64790) - **RHSA-2026:64776** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64776) - **RHSA-2026:64778** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64778) - **RHSA-2026:64781** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64781) - **RHSA-2026:64783** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64783) - **Red Hat VEX** · Important · affected: Red Hat Directory Server 12 · no fix planned: Red Hat Directory Server 12 · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-18355.json)