VulnerabilityPublished 25 Jul 2026Updated 6 Nov 2026

CVE-2026-64289: Linux kernel · iommufd: Set upper bounds on cache invalidation entry_num and entry_len

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in d2bd041e0efaf7d81789779b135279d18b33d6d5 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:51 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in d2bd041e0efaf7d81789779b135279d18b33d6d5, 32ca4aed2a66205b072fcfecabe220289a8149ff, 4d70986002f2f3eaaed89124fb2522bded38b016 +1

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to d2bd041e0efaf7d81789779b135279d18b33d6d5, 32ca4aed2a66205b072fcfecabe220289a8149ff, 4d70986002f2f3eaaed89124fb2522bded38b016 or 2c6381d90898089287e0a358f06f89f6b4b389f2.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 8c6eabae3807e048b9f17733af5e20500fbf858c, < d2bd041e0efaf7d81789779b135279d18b33d6d5	Fixed in d2bd041e0efaf7d81789779b135279d18b33d6d5
LinuxLinux	Affected ≥ 8c6eabae3807e048b9f17733af5e20500fbf858c, < 32ca4aed2a66205b072fcfecabe220289a8149ff	Fixed in 32ca4aed2a66205b072fcfecabe220289a8149ff
LinuxLinux	Affected ≥ 8c6eabae3807e048b9f17733af5e20500fbf858c, < 4d70986002f2f3eaaed89124fb2522bded38b016	Fixed in 4d70986002f2f3eaaed89124fb2522bded38b016
LinuxLinux	Affected ≥ 8c6eabae3807e048b9f17733af5e20500fbf858c, < 2c6381d90898089287e0a358f06f89f6b4b389f2	Fixed in 2c6381d90898089287e0a358f06f89f6b4b389f2
LinuxLinux	Affected =6.8	Fixed in–

AI-suggested

This vulnerability has been fixed in the Linux kernel. The fix caps entry_len under PAGE_SIZE and entry_num under 2^19 in the ioctl handler, preventing excessive CPU locking. Users and administrators should update to the fixed kernel versions identified by the commits d2bd041e0efaf7d81789779b135279d18b33d6d5, 32ca4aed2a66205b072fcfecabe220289a8149ff, 4d70986002f2f3eaaed89124fb2522bded38b016, and 2c6381d90898089287e0a358f06f89f6b4b389f2. No additional mitigation is required beyond applying these official fixes.

Description

CVE-2026-64289 is a vulnerability in the Linux kernel's iommufd component where user-controlled values for cache invalidation parameters entry_num and entry_len were only bounded by U32_MAX. Excessively large values could cause the kernel to perform long, uninterruptible operations, potentially triggering a soft-lockup watchdog and CPU pinning due to non-preemptible kernel execution. The issue is fixed by capping entry_len below PAGE_SIZE and entry_num below 2^19, limiting the size and iteration count of invalidation requests.

Impact

Exploitation of this vulnerability can cause a soft-lockup in the Linux kernel, effectively pinning the CPU and causing denial of service due to the kernel's non-preemptible execution path during cache invalidation. This can degrade system responsiveness or cause system hangs. There is no indication of privilege escalation or data corruption from the provided data.

Summary

The Linux kernel's iommufd_hwpt_invalidate() function previously accepted user-supplied entry_num and entry_len parameters bounded only by U32_MAX. An entry_len larger than the kernel's expected struct size caused the copy helper to scan excess bytes in a single uninterruptible pass, potentially over multi-gigabyte zeroed user memory, triggering a soft-lockup watchdog. A large entry_num drove a backend invalidation loop without rescheduling, causing CPU pinning on a non-preemptible kernel path. The fix introduces upper bounds on entry_len (below PAGE_SIZE) and entry_num (below 2^19), constraining the per-call loop length and preventing excessive CPU locking.

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Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 16:51 UTC

Technical details

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