Kernel memory disclosure via verifier path omission
Published Jun 23, 2021 · Updated Nov 11, 2025
Information disclosure in the Linux kernel before 5.12.13 allows local users to read arbitrary kernel memory via an eBPF program. The eBPF verifier skips ISA-unreachable branch outcomes, allowing a mispredicted path to replace a validated pointer with an attacker-controlled scalar before a speculative load. An unprivileged local user must train the branch predictor and use a cache side channel; the demonstrated consequence is disclosure of kernel and physical memory, not memory modification.
Summary
What happened
Information disclosure in the Linux kernel before 5.12.13 allows local users to read arbitrary kernel memory via an eBPF program. The eBPF verifier skips ISA-unreachable branch outcomes, allowing a mispredicted path to replace a validated pointer with an attacker-controlled scalar before a speculative load. An unprivileged local user must train the branch predictor and use a cache side channel; the demonstrated consequence is disclosure of kernel and physical memory, not memory modification.
The record
- CVE
- CVE-2021-33624
- Published
- Jun 23, 2021
- Updated
- Nov 11, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-843
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 23, 2021CVE publishedPublication date reported by the CVE source.
- Nov 11, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
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
- Proof of Concept for CVE-2021-33624proof of concept · demonstrated
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Technologies
Your stack
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Your stack
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