CVE-2026-11610

Summary

A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). After a successful SASL bind with integrity protection (SSF > 0), an authenticated attacker can send a specially crafted oversized LDAP UNBIND packet that is copied into a 512-byte heap receive buffer without a bounds check in sasl_io_recv() in sasl_io.c. This allows up to approximately 2 megabytes of attacker-controlled data to overflow the buffer, causing a denial of service (server crash). In FreeIPA and Red Hat Identity Management deployments, any domain user with a valid Kerberos ticket, any enrolled host, or any service account can trigger this vulnerability over the network after authenticating via GSSAPI. The vulnerable code path has existed since approximately 2013 (389-ds-base 1.3.2) and was not addressed by the CVE-2025-14905 fix, which patched a separate heap overflow in schema.c only.

Affected Software

VendorProductVersion RangeStatus
Red HatRed Hat Directory Server 11.5 E4S for RHEL 88060020260702180044.0ca98e7e < *unaffected
Red HatRed Hat Directory Server 11.7 E4S for RHEL 88080020260702180836.f969626e < *unaffected
Red HatRed Hat Directory Server 11.9 for RHEL 88100020260702145313.37ed7c03 < *unaffected
Red HatRed Hat Directory Server 12.4 E4S for RHEL 99040020260703055735.1674d574 < *unaffected
Red HatRed Hat Enterprise Linux 100:3.2.0-8.el10_2 < *unaffected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Support0:1.3.11.1-13.el7_9 < *unaffected
Red HatRed Hat Enterprise Linux 88100020260626120929.25e700aa < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support8040020260629123121.96015a92 < *unaffected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On8040020260629123121.96015a92 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support8060020260626130540.824efc52 < *unaffected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On8060020260626130540.824efc52 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Service8080020260630025241.6dbb3803 < *unaffected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutions8080020260630025241.6dbb3803 < *unaffected
Red HatRed Hat Enterprise Linux 90:2.8.0-8.el9_8 < *unaffected
Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutions0:2.4.5-26.el9_4 < *unaffected

Weaknesses

  • CWE-122: Heap-based Buffer Overflow

Workarounds

There is no complete workaround for this flaw. Mitigations that reduce exposure:

  1. Restrict network access to LDAP ports (389/636) to trusted networks only. Note: In FreeIPA/IdM deployments, enrolled clients require LDAP access and this may not be practical.
  2. If DIGEST-MD5 is not required, disable it via nsslapd-allowed-sasl-mechanisms in cn=config. GSSAPI/Kerberos cannot be disabled in FreeIPA/IdM without breaking domain authentication.
  3. Monitor for oversized LDAP UNBIND packets (standard UNBIND is 7 bytes; alert on UNBIND packets exceeding ~100 bytes).
  4. Lowering nsslapd-maxbersize reduces maximum overflow size but does not eliminate the vulnerability.

References