CVE-2026-68388: smb/client: handle overlapping allocated ranges in fallocate
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.5%
EPSS score, percentile 43.7 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 9.8 Critical
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- from 5.10.50 to before 5.10.265
- from 5.12.17 to before 5.13
- 5.14
Unaffected before 5.14; 5.10.265; 5.15.216; 6.1.183; 6.6.148; 6.12.101; and 3 more
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from c406bb9ece6e to before aeb58a4eb39a |
| Affected | from 966a3cb7c7db to before 017198832355 |
| Affected | from 966a3cb7c7db to before f47c7277c03a |
| Affected | from 966a3cb7c7db to before 437637f5ff3f |
| Affected | from 966a3cb7c7db to before 377fe3e583e4 |
| Affected | from 966a3cb7c7db to before 7e08ab7a061b |
| Affected | from 966a3cb7c7db to before a4a09e514283 |
| Affected | from 966a3cb7c7db to before b09ae45d85dc |
| Affected | 2f9f4a2d0e6f |
| Affected | 5e397c943424 |
| Affected | from 5.10.50 to before 5.10.265 |
| Affected | from 5.12.17 to before 5.13 |
Versions not listed are: unaffected.
And 1 more version entries in the CVE record.
| Status | Versions |
|---|---|
| Affected | 5.14 |
| Unaffected | before 5.14 |
| Unaffected | 5.10.265 |
| Unaffected | 5.15.216 |
| Unaffected | 6.1.183 |
| Unaffected | 6.6.148 |
| Unaffected | 6.12.101 |
| Unaffected | 6.18.42 |
| Unaffected | 7.1.6 |
| Unaffected | 7.2 |
Versions not listed are: affected.
Versions the record lists as unaffected: 5.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101, 6.18.42, 7.1.6, 7.2.
Source: CVE List, as of . About the data.
About this vulnerability
In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlapping allocated ranges in fallocate smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC.…
Summary: CVE record, as of .
- CISA has not added CVE-2026-68388 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 10 Aug 2026.
- The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.5% (percentile 43.7), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact total.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
smb/client: handle overlapping allocated ranges in fallocate
In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlapping allocated ranges in fallocate smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC. The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset. For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200): Request: [100, 400) Server range: [ 0, 200) allocated Correct: [100, 200) allocated data, skip [200, 400) hole, zero-fill Current: [100, 300) skipped [300, 400) zero-filled afterwards The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled. Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows. This also prevents a malformed range length from causing an out-of-bounds zero-buffer read.
Source: CVE List, as of . About the data.
Weakness
CWE-125
- CWE-125: Out-of-bounds Read
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
References
8
Known exploited Linux vulnerabilities
- CVE-2026-46300: Linux Kernel Missing Initialization of a Variable Vulnerability
- CVE-2025-39682: Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
- CVE-2025-39964: Linux Kernel Race Condition Vulnerability
- CVE-2026-53266: Linux Kernel Out-of-Bounds Write Vulnerability
- CVE-2026-53362: Linux Kernel Unspecified Vulnerability