Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2025-21687 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 14th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-21687 is a vulnerability in the Linux kernel's VFIO platform module, which handles device passthrough for virtual machines. The issue stems from insufficient bounds checking on the count and offset parameters passed from user space during read and write syscalls. While the offset is capped at 40 bits, the count is not validated, enabling out-of-bounds reads and writes beyond the allocated device memory region. This flaw is classified under CWE-125 (Out-of-bounds Read) and CWE-787 (Out-of-bounds Write), with a CVSS v3.1 base score of 7.8.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low complexity (AC:L) and no user interaction required (UI:N). Successful exploitation allows high-impact arbitrary reads and writes (C:H/I:H/A:H) on the targeted device memory without elevating privileges (S:U), potentially leading to kernel memory corruption, data leakage, or denial of service.
Mitigation involves applying the upstream kernel patches available in the referenced stable branch commits, including 1485932496a1b025235af8aa1e21988d6b7ccd54, 665cfd1083866f87301bbd232cb8ba48dcf4acce, 6bcb8a5b70b80143db9bf12dfa7d53636f824d53, 92340e6c5122d823ad064984ef7513eba9204048, and 9377cdc118cf327248f1a9dde7b87de067681dc9, which add proper bounds checks for both count and offset parameters.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-2636
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: vfio/platform: check the bounds of read/write syscalls count and offset are passed from user space and not checked, only offset is capped to 40 bits, which can be used to…
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read/write out of bounds of the device.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.
Requiring documented secure-development standards and tools can mandate bounds-checked coding practices that avoid the weakness.
Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.
Memory-protection mechanisms limit the exploitability and blast radius of a successful out-of-bounds write.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.
Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.
Routine patching replaces vulnerable code containing out-of-bounds read flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.
Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.
Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.