Remote denial of service via unbounded op count
Published Nov 21, 2025 · Updated Aug 5, 2026
Denial of service in Linux NFSD 6.17 through 6.17.7 allows remote attackers to exhaust kernel memory via an NFSv4 COMPOUND request. The NFSv4 XDR decoder trusts the header's 32-bit operation count and uses it to allocate an uncapped, zeroed COMPOUND operation array. NFSD must be listening and the client's address must pass the export ACL; one request can cause reclaim stalls, OOM kills, or an indefinite NFSD hang.
Summary
What happened
Denial of service in Linux NFSD 6.17 through 6.17.7 allows remote attackers to exhaust kernel memory via an NFSv4 COMPOUND request. The NFSv4 XDR decoder trusts the header's 32-bit operation count and uses it to allocate an uncapped, zeroed COMPOUND operation array. NFSD must be listening and the client's address must pass the export ACL; one request can cause reclaim stalls, OOM kills, or an indefinite NFSD hang.
The record
- CVE
- CVE-2025-40210
- Published
- Nov 21, 2025
- Updated
- Aug 5, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 21, 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=48aab1606fa80027143a445224f552b4eeea845b <3e7f011c255582d7c914133785bbba1990441713
- Affected versionversion=48aab1606fa80027143a445224f552b4eeea845b <b3ee7ce432289deac87b9d14e01f2fe6958f7f0b
- Affected versionversion=6.17
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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