CVE-2026-18355: 389-ds-base: 389-ds-base: heap buffer overflow via sasl wrapped-record length lower-bound underflow in sasl_io_start_packet()

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-07 · updated 2026-10-08
Weakness: CWE-191

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 products

Red Hat Directory Server 11.5 E4S for RHEL 8: all versions — fixed in 8060020260908152739.0ca98e7e
Red Hat Directory Server 11.7 E4S for RHEL 8: all versions — fixed in 8080020260903102346.f969626e
Red Hat Directory Server 11.9 for RHEL 8: all versions — fixed in 8100020260904171440.37ed7c03
Red Hat Directory Server 12: all versions
Red Hat Directory Server 12.2 E4S for RHEL 9: all versions — fixed in 9020020260903155914.1674d574
Red Hat Directory Server 12.4 E4S for RHEL 9: all versions — fixed in 9040020260903102623.1674d574
Red Hat Directory Server 13.2: all versions — fixed in 1788851765
Red Hat Enterprise Linux 10: all versions — fixed in 0:3.2.0-10.el10_2
Red Hat Enterprise Linux 10.0 Extended Update Support: all versions — fixed in 0:3.0.6-21.el10_0
Red Hat Enterprise Linux 7 Extended Lifecycle Support: all versions — fixed in 0:1.3.11.1-15.el7_9
Red Hat Enterprise Linux 8: all versions — fixed in 8100020260904155442.25e700aa
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support: all versions — fixed in 8040020260901171549.96015a92
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On: all versions — fixed in 8040020260901171549.96015a92
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support: all versions — fixed in 8060020260901145727.824efc52
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On: all versions — fixed in 8060020260901145727.824efc52
Red Hat Enterprise Linux 8.8 Telecommunications Update Service: all versions — fixed in 8080020260831180218.6dbb3803
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions: all versions — fixed in 8080020260831180218.6dbb3803
Red Hat Enterprise Linux 9: all versions — fixed in 0:2.8.0-10.el9_8
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions: all versions — fixed in 0:2.2.4-22.el9_2
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: all versions — fixed in 0:2.4.5-29.el9_4
Red Hat Enterprise Linux 9.6 Extended Update Support: all versions — fixed in 0:2.6.1-24.el9_6

How to fix

Upgrade to a fixed version: Red Hat Directory Server 11.5 E4S for RHEL 8 8060020260908152739.0ca98e7e; Red Hat Directory Server 11.7 E4S for RHEL 8 8080020260903102346.f969626e; Red Hat Directory Server 11.9 for RHEL 8 8100020260904171440.37ed7c03; Red Hat Directory Server 12.2 E4S for RHEL 9 9020020260903155914.1674d574; Red Hat Directory Server 12.4 E4S for RHEL 9 9040020260903102623.1674d574; Red Hat Directory Server 13.2 1788851765; Red Hat Enterprise Linux 10 0:3.2.0-10.el10_2; Red Hat Enterprise Linux 10.0 Extended Update Support 0:3.0.6-21.el10_0; Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.3.11.1-15.el7_9; Red Hat Enterprise Linux 8 8100020260904155442.25e700aa; Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 8040020260901171549.96015a92; Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 8040020260901171549.96015a92. Check the vendor advisory for mitigations.

References

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