Kernel compromise via AX.25 refcount underflow
Published Feb 27, 2025 · Updated Aug 5, 2026
Use-after-free in the Linux kernel AX.25 subsystem allows local users to compromise the kernel through an unprivileged socket sequence. The ax25_setsockopt() path binds an AX.25 device through SO_BINDTODEVICE without taking the device references that ax25_release() later drops, causing deterministic refcount underflow and premature frees. Any local unprivileged user on a host with AX.25 already configured can repeat the sequence to disclose kernel memory, corrupt kernel state, or crash the host.
Summary
What happened
Use-after-free in the Linux kernel AX.25 subsystem allows local users to compromise the kernel through an unprivileged socket sequence. The ax25_setsockopt() path binds an AX.25 device through SO_BINDTODEVICE without taking the device references that ax25_release() later drops, causing deterministic refcount underflow and premature frees. Any local unprivileged user on a host with AX.25 already configured can repeat the sequence to disclose kernel memory, corrupt kernel state, or crash the host.
The record
- CVE
- CVE-2025-21792
- Published
- Feb 27, 2025
- Updated
- Aug 5, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 27, 2025CVE publishedPublication date reported by the CVE source.
- Aug 5, 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=4.14.277 <4.15
- Affected versionversion=4.19.240 <4.20
- Affected versionversion=452ae92b99062d2f6a34324eaf705a3b7eac9f8b
- Affected versionversion=5.10.112 <5.11
- Affected versionversion=5.15.35 <5.16
- Affected versionversion=5.17.2 <5.18
- Affected versionversion=5.18
- Affected versionversion=534156dd4ed768e30a43de0036f45dca7c54818f
- Affected versionversion=5.4.190 <5.5
- Affected versionversion=9e1e088a57c23251f1cfe9601bbd90ade2ea73b9
- Affected versionversion=9fd75b66b8f68498454d685dc4ba13192ae069b0 <470bda72fda0fcf54300466d70ce2de62f7835d2
- Affected versionversion=9fd75b66b8f68498454d685dc4ba13192ae069b0 <90056ece99966182dc0e367f3fd2afab46ada847
- Affected versionversion=9fd75b66b8f68498454d685dc4ba13192ae069b0 <94a0de224ed52eb2ecd4f4cb1b937b674c9fb955
- Affected versionversion=9fd75b66b8f68498454d685dc4ba13192ae069b0 <b58f7ca86a7b8e480c06e30c5163c5d2f4e24023
- Affected versionversion=9fd75b66b8f68498454d685dc4ba13192ae069b0 <bca0902e61731a75fc4860c8720168d9f1bae3b6
- Affected versionversion=b20a5ab0f5fb175750c6bafd4cf12daccf00c738
- Affected versionversion=c44a453ffe16eb08acdc6129ac4fa0192dbc0456
- Affected versionversion=de55a1338e6a48ff1e41ea8db1432496fbe2a62b
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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