CVE-2026-90011

CRITICAL CVSS 9.1

Published: 2026-09-16

Modified: 2026-09-16

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AI Threat Summary

CVE-2026-90011 is a moderate vulnerability affecting the target software. Authentication can be bypassed allowing unauthenticated access. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: target: iscsi: Reserve a terminator byte for the login payload iscsi_target_check_login_request() rejects a login PDU whose DataSegmentLength exceeds MAX_KEY_VALUE_PAIRS, but the test is '>' and login->req_buf is allocated with exactly MAX_KEY_VALUE_PAIRS bytes. Since iscsit_get_login_rx() receives payload_length + padding bytes, where padding = ((-payload_length) & 3); any payload_length from 8189 to 8192 fills the whole 8192 byte buffer. The write stays in bounds, but no byte is left for a NUL terminator. The buffer is subsequently consumed as a C string. In the CHAP path chap_check_algorithm() calls kstrdup(a_str), and extract_param() calls strstr(in_buf, pattern) followed by strlen_semi(), none of which take a length. convert_null_to_semi() additionally rewrites every embedded NUL to ';', so even a payload made of well formed NUL separated key=value records is left without a terminator. These walk past the end of the object into adjacent slab memory. It is reachable by an unauthenticated initiator against a portal configured for CHAP; when authentication is not required iscsi_login_zero_tsih_s2() rewrites AuthMethod to None and the CHAP path is never entered. Allocate one extra byte. kzalloc() zeroes it and nothing ever writes to it, as every writer copies to offset 0 for at most MAX_KEY_VALUE_PAIRS bytes, so the buffer is always terminated.

Attack Chain

Reconnaissance

Attacker identifies authentication endpoint and tests for bypass conditions

Initial Access

Attacker exploits CVE-2026-90011 authentication flaw to gain unauthorized access without valid credentials

Discovery

Attacker enumerates accessible resources, users, and configurations

Collection

Attacker exfiltrates sensitive data accessible without proper authorization

MITRE ATT&CK Techniques

T1078 Valid Accounts

Initial Access

Authentication bypass grants attacker access as legitimate user

T1548 Abuse Elevation Control Mechanism

Privilege Escalation

Bypassed auth may grant elevated or admin-level permissions

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-2026-90011
CVSS Score	9.1
Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`
Published	2026-09-16
Exploited	No
CISA KEV	No
PoC	Not public

References

External Resources

NVD Entry BleepingComputer The Hacker News