Kernel memory corruption via undersized USB notification fragment
Published Feb 22, 2025 · Updated May 12, 2026
Improper input validation in the Linux kernel CDC-ACM driver allows physically proximate attackers to corrupt kernel memory via USB. In acm_ctrl_irq(), an undersized first notification fragment is used to read length data beyond the received buffer, allowing expected_size minus nb_index to wrap during reassembly. The path runs only after userspace opens the ttyACM device, although ModemManager can open a matching device automatically.
Summary
What happened
Improper input validation in the Linux kernel CDC-ACM driver allows physically proximate attackers to corrupt kernel memory via USB. In acm_ctrl_irq(), an undersized first notification fragment is used to read length data beyond the received buffer, allowing expected_size minus nb_index to wrap during reassembly. The path runs only after userspace opens the ttyACM device, although ModemManager can open a matching device automatically.
The record
- CVE
- CVE-2025-21704
- Published
- Feb 22, 2025
- Updated
- May 12, 2026
- Vendor
- Siemens
- Product
- SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
- Classifications
- CWE-20, T1200
- Attack vector
- physical
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 22, 2025CVE publishedPublication date reported by the CVE source.
- May 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=0 <*
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Published CVSS scores
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Attacks
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Technologies
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