CVE-2026-62648 Overview
CVE-2026-62648 affects Siemens Reyrolle 7SR5 protection relays in all versions prior to V2.70. The device fails to properly validate the length of the URL component in pre-authenticated HTTP messages before appending additional data. This flaw produces an out-of-bounds write condition [CWE-787] in memory. An unauthenticated remote attacker can send a crafted HTTP request to crash the device, forcing a reboot and creating a denial-of-service condition. Reyrolle 7SR5 units serve as digital protection relays in electrical substations, so a forced reboot can disrupt monitoring and protection functions during the outage window.
Critical Impact
Unauthenticated remote attackers can crash Reyrolle 7SR5 relays over the network, triggering reboots and disrupting substation protection availability.
Affected Products
- Siemens Reyrolle 7SR5 — all versions prior to V2.70
- Digital protection relay firmware exposing pre-authenticated HTTP services
- Deployments running affected firmware in substation automation networks
Discovery Timeline
- 2026-09-08 - CVE-2026-62648 published to NVD
- 2026-09-08 - Last updated in NVD database
- Vendor advisory - Siemens Security Advisory SSA-142885
Technical Details for CVE-2026-62648
Vulnerability Analysis
The Reyrolle 7SR5 embedded HTTP server processes URL fields inside HTTP request messages before authentication. The server appends additional data to the URL component without first validating its length against the destination buffer size. When the combined data exceeds the buffer bounds, the write operation corrupts adjacent memory, and the device faults into a reboot.
Because the flaw is triggered pre-authentication, no credentials or user interaction are required. A single crafted HTTP request over the network is sufficient to induce the crash. The vulnerability affects availability only; the CVSS vector reports no impact to confidentiality or integrity. Repeated exploitation can produce sustained loss of protection and control functionality in the affected substation asset.
Root Cause
The root cause is missing length validation on an untrusted input field, classified as an out-of-bounds write [CWE-787]. The HTTP parser treats the URL length as safe and performs an append operation that writes past the allocated buffer. This is a classic input-validation failure at a security boundary that should reject or truncate oversized fields.
Attack Vector
Exploitation requires network reachability to the HTTP interface of the Reyrolle 7SR5 device. The attacker sends an HTTP message containing a URL component crafted to trigger the append operation past buffer bounds. No authentication, privileges, or user interaction are needed. Successful exploitation crashes the device and forces a reboot, producing a denial-of-service state. Siemens describes the technical detail in the SSA-142885 advisory; no public proof-of-concept is available.
Detection Methods for CVE-2026-62648
Indicators of Compromise
- Unexpected reboots or watchdog resets on Reyrolle 7SR5 relays without operator action
- HTTP requests to the relay containing abnormally long URL components or malformed request lines
- Loss of communication with the relay from substation SCADA or engineering workstations followed by device recovery
- Repeated short-interval device availability gaps that correlate with inbound HTTP traffic
Detection Strategies
- Inspect network traffic destined for Reyrolle 7SR5 management interfaces for HTTP requests with oversized URL fields
- Alert on HTTP requests from unexpected source addresses to substation protection devices
- Correlate device reboot syslog or SNMP trap events with preceding HTTP traffic to the same host
- Baseline normal engineering-access patterns and flag deviations targeting the HTTP service
Monitoring Recommendations
- Forward device syslog, SNMP traps, and availability metrics into a centralized SIEM for correlation
- Monitor OT network segments with protocol-aware intrusion detection tuned for HTTP anomalies
- Track firmware versions across the Reyrolle 7SR5 fleet to identify unpatched units still below V2.70
- Enable alerting on repeated TCP resets or session terminations against the relay HTTP port
How to Mitigate CVE-2026-62648
Immediate Actions Required
- Upgrade Reyrolle 7SR5 firmware to V2.70 or later as instructed in Siemens SSA-142885
- Restrict network access to the relay HTTP interface to authorized engineering hosts only
- Place affected devices behind an OT firewall segmented from corporate IT and internet-exposed networks
- Audit current firmware inventory to identify all vulnerable Reyrolle 7SR5 units
Patch Information
Siemens addresses CVE-2026-62648 in Reyrolle 7SR5 firmware V2.70. Operators should schedule firmware upgrades during planned maintenance windows and validate device functionality after the update. Refer to Siemens Security Advisory SSA-142885 for the authoritative patch procedure and any additional model-specific guidance.
Workarounds
- Apply Siemens' defense-in-depth guidance for industrial security and isolate the relay HTTP service from untrusted networks
- Disable or block the HTTP management service on network paths where operational use is not required
- Enforce access control lists on switches and firewalls to permit only engineering workstations to reach the relay
- Increase monitoring of device availability until firmware V2.70 is deployed across the fleet
# Configuration example: restrict HTTP access to Reyrolle 7SR5 on an upstream firewall
# Replace RELAY_IP and ENG_WORKSTATION with site-specific values
iptables -A FORWARD -p tcp -s ENG_WORKSTATION -d RELAY_IP --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d RELAY_IP --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
