CVE-2026-18355

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, 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 Software

VendorProductVersion RangeStatus
Red HatRed Hat Directory Server 11.7 E4S for RHEL 88080020260903102346.f969626e < *unaffected
Red HatRed Hat Directory Server 11.9 for RHEL 88100020260904171440.37ed7c03 < *unaffected
Red HatRed Hat Directory Server 12.2 E4S for RHEL 99020020260903155914.1674d574 < *unaffected
Red HatRed Hat Directory Server 12.4 E4S for RHEL 99040020260903102623.1674d574 < *unaffected
Red HatRed Hat Enterprise Linux 100:3.2.0-10.el10_2 < *unaffected
Red HatRed Hat Enterprise Linux 10.0 Extended Update Support0:3.0.6-21.el10_0 < *unaffected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Support0:1.3.11.1-15.el7_9 < *unaffected
Red HatRed Hat Enterprise Linux 88100020260904155442.25e700aa < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support8040020260901171549.96015a92 < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On8040020260901171549.96015a92 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support8060020260901145727.824efc52 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On8060020260901145727.824efc52 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Service8080020260831180218.6dbb3803 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutions8080020260831180218.6dbb3803 < *unaffected
Red HatRed Hat Enterprise Linux 90:2.8.0-10.el9_8 < *unaffected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutions0:2.2.4-22.el9_2 < *unaffected
Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutions0:2.4.5-29.el9_4 < *unaffected
Red HatRed Hat Enterprise Linux 9.6 Extended Update Support0:2.6.1-24.el9_6 < *unaffected
Red HatRed Hat Directory Server 13.21788851765 < *unaffected

Weaknesses

  • CWE-191: Integer Underflow (Wrap or Wraparound)

Workarounds

Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

References