Quick answers
- Is CVE-2026-18355 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18355 being exploited in the wild.
- How severe is CVE-2026-18355?
- High severity, with a CVSS score of 7.5, published 7 September 2026.
- Which products and versions are affected?
- Red Hat 389 Directory Server.
- Is there a fix for CVE-2026-18355?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-18355 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-18355?
- Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A heap buffer overflow exists in the sasl_io_start_packet() and sasl_io_read_packet() functions of 389 Directory Server's SASL I/O layer. The vulnerability is triggered when the wrapped-record length from the wire is validated only against an upper bound; a small wire length (0, 1, or 2 bytes) causes an integer underflow in the encrypted_buffer_count calculation, leading to PR_Recv attempting to read approximately 4 GiB into a 1024-byte heap buffer. The attack requires prior successful SASL authentication with integrity protection (SSF > 0), meaning the attacker must be a valid directory user. An attacker can achieve denial of service by crashing the server or potentially remote code execution via heap corruption with attacker-controlled data. Patches are available from Red Hat.
Affected products
- Red Hat 389 Directory Server
Timeline
- 2026-09-07: disclosed