Linux: Out-of-bounds Read
CVE-2026-63938 is a critical-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 9.3 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions 5198f70c09a5f6e9e5f5a0a2c6b388f24294b176, 75c8d1d7291268b479794fba5808971dc2f5eaf3, 505a3b94535583e4265360e2621734e355ef263d as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.2% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 5198f70c09a5f6e9e5f5a0a2c6b388f24294b176 or 75c8d1d7291268b479794fba5808971dc2f5eaf3 or 505a3b94535583e4265360e2621734e355ef263d or 121d88de56bc5c0ba0ce2f6381af67f948a7e7c1, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.93 or 6.18.35 or 7.0.12, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 9b54e248d2644be71cb394eb85f31ad99e023a05 up to, but not including, 5198f70c09a5f6e9e5f5a0a2c6b388f24294b176; 9b54e248d2644be71cb394eb85f31ad99e023a05 up to, but not including, 75c8d1d7291268b479794fba5808971dc2f5eaf3; 9b54e248d2644be71cb394eb85f31ad99e023a05 up to, but not including, 505a3b94535583e4265360e2621734e355ef263d; 9b54e248d2644be71cb394eb85f31ad99e023a05 up to, but not including, 121d88de56bc5c0ba0ce2f6381af67f948a7e7c1; 6.11 | 5198f70c09a5f6e9e5f5a0a2c6b388f24294b176, 75c8d1d7291268b479794fba5808971dc2f5eaf3, 505a3b94535583e4265360e2621734e355ef263d, 121d88de56bc5c0ba0ce2f6381af67f948a7e7c1 |
| Linux | Linux Kernel | 6.11 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.1 | 6.12.93, 6.18.35, 7.0.12 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Check PSC request indices against the actual size of the buffer When processing Page State Change (PSC) requests, validate the PSC buffer against the effective size of the scratch area, which could be less than the maximum size if the guest provided a pointer that isn't exactly at the start of the GHCB shared buffer.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.8 High severity
- 7.3 High severity
- 7.1 High severity
- 7.8 High severity
- 9.8 Critical severity
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