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CVE-2017-6026: Schneider Electric Modicon M251 Firmware: Use of Insufficiently Random Values

CVE-2017-6026 is rated critical with a CVSS v3.1 base score of 9.1 and affects Schneider Electric Modicon M251 Firmware. Per its scoring, it can be exploited over the network, without authentication, without any user interaction.

Vulnerability description

A Use of Insufficiently Random Values issue was discovered in Schneider Electric Modicon PLCs Modicon M241, firmware versions prior to Version 4.0.5.11, and Modicon M251, firmware versions prior to Version 4.0.5.11. The session numbers generated by the web application are lacking randomization and are shared between several users. This may allow a current session to be compromised.

Severity breakdown

CVSS v3.1 9.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

• Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
• Attack complexity: Low. No special conditions; the attack can be repeated reliably.
• Privileges required: None. No account or prior access is needed.
• User interaction: None. No action from any user is needed.
• Scope: Unchanged. Impact stays within the vulnerable component.
• Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
• Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
• Availability impact: None. No effect on availability.

Underlying weakness

CWE-330: Use of Insufficiently Random Values

The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Affected products

• Schneider Electric Modicon M251 Firmware: up to and including 4.0.3.20
• Schneider Electric Modicon M241 Firmware: up to and including 4.0.3.20

References

• http://www.securityfocus.com/bid/97254
• https://ics-cert.us-cert.gov/advisories/ICSA-17-089-02
• https://www.exploit-db.com/exploits/45918/