CVE-2026-18355: Red Hat Directory Server 11.5 e4s For Rhel 8
High severity, CVSS 7.5. EPSS: 0.8% chance of exploitation in the next 30 days.
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 Red Hat Directory Server 11.5 e4s For Rhel 8: before 8060020260908152739.0ca98e7e (fixed in 8060020260908152739.0ca98e7e)
- Red Hat Red Hat Directory Server 11.7 e4s For Rhel 8: before 8080020260903102346.f969626e (fixed in 8080020260903102346.f969626e)
- Red Hat Red Hat Directory Server 11.9 For Rhel 8: before 8100020260904171440.37ed7c03 (fixed in 8100020260904171440.37ed7c03)
- Red Hat Red Hat Directory Server 12
- Red Hat Red Hat Directory Server 12.2 e4s For Rhel 9: before 9020020260903155914.1674d574 (fixed in 9020020260903155914.1674d574)
- Red Hat Red Hat Directory Server 12.4 e4s For Rhel 9: before 9040020260903102623.1674d574 (fixed in 9040020260903102623.1674d574)
- Red Hat Red Hat Directory Server 13
- Red Hat Red Hat Directory Server 13.2: before 1788851765 (fixed in 1788851765)
- Red Hat Red Hat Enterprise Linux 10: before 0:3.2.0-10.el10_2 (fixed in 0:3.2.0-10.el10_2)
- Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support: before 0:3.0.6-21.el10_0 (fixed in 0:3.0.6-21.el10_0)
- Red Hat Red Hat Enterprise Linux 6
- Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support: before 0:1.3.11.1-15.el7_9 (fixed in 0:1.3.11.1-15.el7_9)
- Red Hat Red Hat Enterprise Linux 8: before 8100020260904155442.25e700aa (fixed in 8100020260904155442.25e700aa)
- Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support: before 8040020260901171549.96015a92 (fixed in 8040020260901171549.96015a92)
- Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On: before 8040020260901171549.96015a92 (fixed in 8040020260901171549.96015a92)
- Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support: before 8060020260901145727.824efc52 (fixed in 8060020260901145727.824efc52)
- Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On: before 8060020260901145727.824efc52 (fixed in 8060020260901145727.824efc52)
- Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service: before 8080020260831180218.6dbb3803 (fixed in 8080020260831180218.6dbb3803)
- Red Hat Red Hat Enterprise Linux 8.8 Update Services For SAP Solutions: before 8080020260831180218.6dbb3803 (fixed in 8080020260831180218.6dbb3803)
- Red Hat Red Hat Enterprise Linux 9: before 0:2.8.0-10.el9_8 (fixed in 0:2.8.0-10.el9_8)
- Red Hat Red Hat Enterprise Linux 9.2 Update Services For SAP Solutions: before 0:2.2.4-22.el9_2 (fixed in 0:2.2.4-22.el9_2)
- Red Hat Red Hat Enterprise Linux 9.4 Update Services For SAP Solutions: before 0:2.4.5-29.el9_4 (fixed in 0:2.4.5-29.el9_4)
- Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support: before 0:2.6.1-24.el9_6 (fixed in 0:2.6.1-24.el9_6)
Published 2026-09-07. Last modified 2026-10-08.