sshd Buffer Underflow Error Message Matching CVE-2018-15473 Exploit Attempt (Linux)
Flags Linux sshd pre-auth buffer parsing error messages that align with CVE-2018-15473 exploit attempts.
- Product
- linux
- Service
- sshd
- Author
- Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2017-08-24
- Updated
- 2026-07-31
ATT&CK techniques
ReconResource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags SSH daemon log entries containing a specific pre-auth error message indicating a buffer length mismatch. Attackers may trigger this condition while attempting to exploit CVE-2018-15473, using crafted input to cause malformed parsing behavior. It relies on Linux sshd service logs and matches the presence of the exact error string in log messages.
Reporting behind it
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No changelog recorded for this version.2026-07-30
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: sshd Buffer Underflow Error Message Matching CVE-2018-15473 Exploit Attempt (Linux)
id: 25461ba2-54e6-4227-82b7-3eaeecc07432
status: test
description: This rule flags SSH daemon log entries containing a specific pre-auth error message indicating a buffer length mismatch. Attackers may trigger this condition while attempting to exploit CVE-2018-15473, using crafted input to cause malformed parsing behavior. It relies on Linux sshd service logs and matches the presence of the exact error string in log messages.
references:
- https://github.com/Rhynorater/CVE-2018-15473-Exploit
- https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2018/Exploits/CVE-2018-15473/lnx_sshd_exploit_cve_2018_15473.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2017-08-24
modified: 2021-11-27
tags:
- attack.reconnaissance
- attack.t1589
- cve.2018-15473
- detection.emerging-threats
logsource:
product: linux
service: sshd
detection:
keywords:
- "error: buffer_get_ret: trying to get more bytes 1907 than in buffer 308 [preauth]"
condition: keywords
falsepositives:
- Unknown
level: medium
license: DRL-1.1
related:
- id: 4c9d903d-4939-4094-ade0-3cb748f4d7da
type: derived