Kernel memory access via iptables replacement race
Published May 21, 2023 · Updated Jan 31, 2025
Use-after-free in Linux kernel netfilter before 5.10 allows local users to access freed kernel memory during concurrent iptables rule replacement. The x_tables packet path mishandles its per-CPU sequence count, allowing a reader to retain an object that concurrent ruleset replacement frees. Triggering requires CAP_NET_ADMIN within an unprivileged user namespace; published evidence demonstrates a stale-memory read but not reliable privilege escalation.
Summary
What happened
Use-after-free in Linux kernel netfilter before 5.10 allows local users to access freed kernel memory during concurrent iptables rule replacement. The x_tables packet path mishandles its per-CPU sequence count, allowing a reader to retain an object that concurrent ruleset replacement frees. Triggering requires CAP_NET_ADMIN within an unprivileged user namespace; published evidence demonstrates a stale-memory read but not reliable privilege escalation.
The record
- CVE
- CVE-2020-36694
- Published
- May 21, 2023
- Updated
- Jan 31, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-416
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- May 21, 2023CVE publishedPublication date reported by the CVE source.
- Jan 31, 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.
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.
Weakness, pattern, technique
Public exploit references
- Syzkaller C reproducer for the use-after-freeproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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