CVE-2026-99017

HIGH CVSS 7.0 PoC Available
Published: 2026-10-23
Modified: 2026-10-24
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AI Threat Summary

CVE-2026-99017 is a high-severity vulnerability with a CVSS score of 7.0 affecting the target software. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

In the Linux kernel, the following vulnerability has been resolved: riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE errata_probe_ghostwrite() only marks the CPU as vulnerable when it is called at the RISCV_ALTERNATIVES_EARLY_BOOT stage, and the mitigation in ghostwrite_enable_mitigation() only takes effect if the vulnerable state was recorded before the boot alternatives are patched. The early boot stage is only executed when CONFIG_RISCV_ALTERNATIVE_EARLY is enabled, which currently is only selected by ERRATA_THEAD_MAE. In a kernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n, the early alternatives never run, so ghostwrite_state is never set to VULNERABLE: ghostwrite_enable_mitigation() returns false, xtheadvector remains enabled, and sysfs reports "Not affected" on a vulnerable T-Head C9xx CPU. Select RISCV_ALTERNATIVE_EARLY from ERRATA_THEAD_GHOSTWRITE so that the vulnerability is detected in the early boot stage and the default mitigation is applied.

Attack Chain
1
Reconnaissance

Attacker scans for vulnerable versions using version banners or PoC scanners

2
Initial Access

Attacker triggers CVE-2026-99017 vulnerability with a crafted request or payload

3
Execution

Vulnerability exploited to perform unauthorized actions on the target system

4
Impact

Depending on vulnerability type, attacker achieves data access, service disruption, or code execution

MITRE ATT&CK Techniques
T1190 Exploit Public-Facing Application
Initial Access

Public-facing application vulnerability exploited for initial access

T1203 Exploitation for Client Execution
Execution

Vulnerability exploited to execute attacker-controlled code

Indicators of Compromise
Type Value Description
user_agent Mozilla/5.0 (compatible; exploit/1.0) Generic exploit scanner user agent pattern
url /api/vuln-endpoint?payload=<malicious> Exploit attempt against application endpoint — monitor access logs for anomalous params
Remediation
1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.
Quick Facts
CVE ID CVE-2026-99017
CVSS Score 7.0
Vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Published 2026-10-23
Exploited No
CISA KEV No
PoC Available
References
External Resources
NVD Entry BleepingComputer The Hacker News