Local denial of service via debugfs lock inversion
Published Sep 17, 2026 · Updated Sep 17, 2026
Deadlock in Linux s390 debug support allows local users to hang debugfs writes and module removal by racing a write with unregistration. debug_unregister() holds debug_mutex while debugfs_remove() waits for an active write to finish, but debug_input() needs the same mutex to complete that write. Triggering the cycle requires access to the debugfs file and concurrent debug-area removal on s390; the documented consequence is stalled operations, not data disclosure or modification.
Summary
What happened
Deadlock in Linux s390 debug support allows local users to hang debugfs writes and module removal by racing a write with unregistration. debug_unregister() holds debug_mutex while debugfs_remove() waits for an active write to finish, but debug_input() needs the same mutex to complete that write. Triggering the cycle requires access to the debugfs file and concurrent debug-area removal on s390; the documented consequence is stalled operations, not data disclosure or modification.
The record
- CVE
- CVE-2026-90209
- Published
- Sep 17, 2026
- Updated
- Sep 17, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Sep 17, 2026CVE publishedPublication date reported by the CVE source.
- Sep 17, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=5.10.65 <5.11
- Affected versionversion=5.13.17 <5.14
- Affected versionversion=5.14.4 <5.15
- Affected versionversion=5.15
- Affected versionversion=5.4.146 <5.5
- Affected versionversion=86f9980909f31ab205323eeeb290fe3cbb4952b4
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <183f8f6d64bb0510070c856b9927618c53014a7b
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <445c31ac638fd1af203d79bdf25fc0cb3149fbbc
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <45bb341d1b73eb293e0dd43d9b72bbc8b615d0ba
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <54e1259b75d6402a1d0cfb822b9bb2c507e53dab
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <5d83f3faa3fb7f23f298cfd40382611999de5d1d
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <a08b70ed2d1ec907353a72f15163b8e34ff4b2f8
- Affected versionversion=9372a82892c2caa6bccab9a4081166fa769699f8 <a214c3dacc779b2afcb0ac9c8001e45ee4ffb2ed
- Affected versionversion=c68ba4a708fbd0efdc384cd29250bb292a45e559
- Affected versionversion=e234f66168f0d50c0d28154fb983a14e85c3c526
- Affected versionversion=fe5793e90d3f572a87ba67fe2f0e1679fdff14f8
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- Concurrent vmur debugfs write and module-unload reproducerproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Get started to see how Hinoki identifies affected software and validates exploitability in your environment.
Get started