Kernel crash via multicast join cleanup race
Published Oct 6, 2026 · Updated Oct 6, 2026
A use-after-free in Linux kernel RDMA/ucma allows local users to cause a kernel crash through concurrent multicast joins. In ucma_process_join(), the failed copy_to_user() path drops ctx->mutex before cleanup, allowing a second same-address join to make leave-by-address remove the wrong entry while queued RoCE work reads the freed object. The trigger requires local access to the RDMA user connection-manager interface and a failed response copy; the reported consequence is a kernel availability failure.
Summary
What happened
A use-after-free in Linux kernel RDMA/ucma allows local users to cause a kernel crash through concurrent multicast joins. In ucma_process_join(), the failed copy_to_user() path drops ctx->mutex before cleanup, allowing a second same-address join to make leave-by-address remove the wrong entry while queued RoCE work reads the freed object. The trigger requires local access to the RDMA user connection-manager interface and a failed response copy; the reported consequence is a kernel availability failure.
The record
- CVE
- CVE-2026-98253
- Published
- Oct 6, 2026
- Updated
- Oct 6, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- Unavailable
Timeline
How it unfolded
- Oct 6, 2026CVE publishedPublication date reported by the CVE source.
- Oct 6, 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=5.10.20 <5.10.271
- Affected versionversion=5.11.3 <5.12
- Affected versionversion=5.12
- Affected versionversion=60d613b39e8d0c9f3b526e9c96445422b4562d76 <29b9ed83d8bfab5c6e11fcbf1aa836aa4ae26cb9
- Affected versionversion=a3262b3884dd67b4c5632ce7cdf9cff9d1a575d4
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <01cbdb724c584d7772fd25af2e4dfdf8527ce0d5
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <01e29d0d78a8f66f221625720a04939eef5ec1f6
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <43c4e24bd10370fc976f6220518049ce71419399
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <52172e11bd074ccaded21740ffeb67123f01dd00
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <662ade4de9ff5eceb0820a9f8e9fac70ba6a815b
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <83610ee5e498fa5bfcb80031d2b959baea276bf6
- Affected versionversion=fe454dc31e84f8c14cb8942fcb61666c9f40745b <ae805d204cf1f15b87d1bf3529b4c649f3519420
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.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- syzkaller C reproducer for RDMA/ucma use-after-freeproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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