Service interruption via miscast IPv4 routing state
Published Feb 27, 2024 · Updated May 11, 2026
Stack out-of-bounds read in sch_frag in Linux kernel 5.11 before 5.11.20 and 5.12 before 5.12.3 allows local users to interrupt service. sch_fragment() supplies a temporary struct dst_entry for IPv4, but ip_mtu_locked() treats its pointer as struct rtable and reads rt_mtu_locked beyond the stack object. Local low-privileged access and an act_mirred path that fragments IPv4 traffic previously reassembled by act_ct are required; the published reproduction records a KASAN fault.
Summary
What happened
Stack out-of-bounds read in sch_frag in Linux kernel 5.11 before 5.11.20 and 5.12 before 5.12.3 allows local users to interrupt service. sch_fragment() supplies a temporary struct dst_entry for IPv4, but ip_mtu_locked() treats its pointer as struct rtable and reads rt_mtu_locked beyond the stack object. Local low-privileged access and an act_mirred path that fragments IPv4 traffic previously reassembled by act_ct are required; the published reproduction records a KASAN fault.
The record
- CVE
- CVE-2021-46954
- Published
- Feb 27, 2024
- Updated
- May 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 27, 2024CVE publishedPublication date reported by the CVE source.
- May 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=5.11
- Affected versionversion=c129412f74e99b609f0a8e95fc3915af1fd40f34 <018bb8da5b5888e19585f9b802f036afe643fcef
- Affected versionversion=c129412f74e99b609f0a8e95fc3915af1fd40f34 <31fe34a0118e0acc958c802e830ad5d37ef6b1d3
- Affected versionversion=c129412f74e99b609f0a8e95fc3915af1fd40f34 <8e6dfb7beeb6489ac1365b8a71052e737f5da76e
What conditions does exploitation require?
What is affected?
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
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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