Kernel heap overread via short sysfs writes
Published Sep 11, 2026 · Updated Sep 11, 2026
Out-of-bounds read in Linux before 6.18.50 or 7.2.4 allows local users with root access to read past a kernel heap buffer. pci_write_legacy_io() unconditionally loads four bytes from kernfs buffers holding one- or two-byte writes, reading up to two bytes beyond the allocation. The root-only legacy_io file exists only on Alpha and PowerPC; the overread feeds unintended data to PCI I/O space rather than directly disclosing it.
Summary
What happened
Out-of-bounds read in Linux before 6.18.50 or 7.2.4 allows local users with root access to read past a kernel heap buffer. pci_write_legacy_io() unconditionally loads four bytes from kernfs buffers holding one- or two-byte writes, reading up to two bytes beyond the allocation. The root-only legacy_io file exists only on Alpha and PowerPC; the overread feeds unintended data to PCI I/O space rather than directly disclosing it.
The record
- CVE
- CVE-2026-89722
- Published
- Sep 11, 2026
- Updated
- Sep 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Sep 11, 2026CVE publishedPublication date reported by the CVE source.
- Sep 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <6.18.50
- Affected versionversion=0 <7.2.4
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <7a99e9c7011905734cc2739038f2a224b6be0d1f
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <dc76258d0132df1d831a5a29758bd448ca9c566e
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e892f05f1f790d5721cd8e3c561ed76da7e08bae
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
No sourced classifications are available.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
See the directory against your own environment.
Your stack
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