Predictable Session Identifiers in Reyrolle 7SR5 Devices

A vulnerability has been identified in Reyrolle 7SR5 (All versions < V2.70). A random number generator is used to generate security-relevant values (such as session identifiers used for authentication purposes) that is not initialized with a True Random Number Generator (TRNG), resulting in a predictable sequence of generated values. This could allow an unauthenticated remote attacker to more easily predict the generated values and impersonate a legitimate authenticated user, potentially gaining unauthorized access to the device.

Casky was already ahead

This CVE exploits attack patterns that Casky's 323matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

CVE-2026-62647 exploits a critical cryptographic weakness in Reyrolle 7SR5 protective relays (versions prior to V2.70), where session identifiers and other security-relevant values are generated using a pseudo-random number generator (PRNG) instead of a true random number generator (TRNG). This flaw enables unauthenticated remote attackers to predict authentication tokens and session identifiers, effectively bypassing access controls and impersonating legitimate users. Organizations deploying these devices in critical infrastructure environments—particularly in power systems, industrial control networks, and utility operations—face significant risk of unauthorized system access, credential hijacking, and potential operational disruption.

Casky.ai's 323 mapped skills detect the attack patterns underlying this vulnerability by analyzing network traffic and authentication logs against MITRE ATT&CK techniques TA0001 (Reconnaissance) and TA0043 (Reconnaissance). Practitioners using the platform with Claude's extended reasoning will identify indicators such as repeated session identifier patterns, anomalous authentication sequences, and brute-force attempts against predictable token spaces. The system flags CWE-20 (Improper Input Validation) weaknesses by correlating failed authentication attempts with temporally-clustered successful sessions, revealing token prediction attacks. Findings will surface suspicious login patterns from unexpected sources, repeated session reuse within compressed timeframes, and authentication events that deviate from normal user behavior—all hallmarks of an attacker leveraging the PRNG predictability to forge valid credentials.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

323 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-62647.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

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Casky has 323 skills that investigate the attack patterns behind CVE-2026-62647. Run one and get CVSS-scored findings in 3 minutes.

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