CVE-2026-64388

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-07-25. a secondary CVSS source baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

smb/client: fix chown/chgrp with SMB3 POSIX Extensions

Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were also explicitly set.

Fix this by checking for posix_extensions in cifs_setattr_nounix() when updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map and set the ownership/group information on the server.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
2%
KEV
Not listed

Published

July 25, 2026

Last Modified

August 17, 2026

Advisory Details (2)

Auto-updated Jul 27, 2026
No patch confirmed yet.
generic

smb/client: fix chown/chgrp with SMB3 POSIX Extensions - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33
generic

smb/client: fix chown/chgrp with SMB3 POSIX Extensions - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e

Vendor Advisories for CVE-2026-64388(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
linux5.10.103-1 ... 7.2~rc5-1~exp1 (500 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 7.2~rc5-1~exp1 (338 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 7.2~rc5-1~exp1 (162 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 7.1~rc7-1~exp1 (156 versions)7.1.4-1—

Data Freshness Timeline

(refreshed 19× in last 7d / 109× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 137 total refreshes for this CVE.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-30 00:05 UTCEG score recompute
  3. 2026-08-30 00:05 UTCGHSA enrichment
  4. 2026-08-28 21:42 UTCEPSS rescore
  5. 2026-08-27 22:55 UTCEG score recompute
  6. 2026-08-27 22:55 UTCGHSA enrichment
  7. 2026-08-27 10:11 UTCGHSA enrichment
  8. 2026-08-26 21:26 UTCEG score recompute
  9. 2026-08-26 21:26 UTCGHSA enrichment
  10. 2026-08-26 14:47 UTCEPSS rescore
  11. 2026-08-26 08:42 UTCGHSA enrichment
  12. 2026-08-25 19:58 UTCEG score recompute
  13. 2026-08-25 19:58 UTCGHSA enrichment
  14. 2026-08-25 13:49 UTCEPSS rescore
  15. 2026-08-25 07:13 UTCGHSA enrichment
  16. 2026-08-24 18:28 UTCEG score recompute
  17. 2026-08-24 18:28 UTCGHSA enrichment
  18. 2026-08-24 05:41 UTCGHSA enrichment
  19. 2026-08-23 16:57 UTCGHSA enrichment
  20. 2026-08-23 04:13 UTCEG score recompute
  21. 2026-08-23 04:13 UTCGHSA enrichment
  22. 2026-08-23 00:19 UTCEPSS rescore
  23. 2026-08-22 15:28 UTCGHSA enrichment
  24. 2026-08-22 02:43 UTCEG score recompute
  25. 2026-08-22 02:43 UTCGHSA enrichment
Show 75 more
  1. 2026-08-21 23:49 UTCEPSS rescore
  2. 2026-08-21 13:58 UTCGHSA enrichment
  3. 2026-08-21 00:58 UTCEG score recompute
  4. 2026-08-21 00:57 UTCGHSA enrichment
  5. 2026-08-20 22:55 UTCEPSS rescore
  6. 2026-08-20 12:13 UTCGHSA enrichment
  7. 2026-08-19 23:29 UTCEG score recompute
  8. 2026-08-19 23:29 UTCGHSA enrichment
  9. 2026-08-19 17:04 UTCEPSS rescore
  10. 2026-08-19 10:44 UTCGHSA enrichment
  11. 2026-08-18 21:59 UTCEG score recompute
  12. 2026-08-18 21:59 UTCGHSA enrichment
  13. 2026-08-18 13:48 UTCEPSS rescore
  14. 2026-08-18 09:12 UTCGHSA enrichment
  15. 2026-08-17 20:18 UTCEG score recompute
  16. 2026-08-17 20:18 UTCGHSA enrichment
  17. 2026-08-17 13:47 UTCEPSS rescore
  18. 2026-08-17 05:18 UTCEG score recompute
  19. 2026-08-17 05:18 UTCGHSA enrichment
  20. 2026-08-16 22:30 UTCEG score recompute
  21. 2026-08-16 22:30 UTCGHSA enrichment
  22. 2026-08-16 14:56 UTCEPSS rescore
  23. 2026-08-16 09:46 UTCEG score recompute
  24. 2026-08-16 09:46 UTCGHSA enrichment
  25. 2026-08-15 21:02 UTCGHSA enrichment
  26. 2026-08-15 08:18 UTCEG score recompute
  27. 2026-08-15 08:18 UTCGHSA enrichment
  28. 2026-08-15 01:30 UTCEPSS rescore
  29. 2026-08-14 19:34 UTCGHSA enrichment
  30. 2026-08-14 06:50 UTCEG score recompute
  31. 2026-08-14 06:50 UTCGHSA enrichment
  32. 2026-08-13 22:00 UTCEPSS rescore
  33. 2026-08-13 18:05 UTCGHSA enrichment
  34. 2026-08-13 05:20 UTCGHSA enrichment
  35. 2026-08-12 16:36 UTCEG score recompute
  36. 2026-08-12 16:36 UTCGHSA enrichment
  37. 2026-08-12 13:51 UTCEPSS rescore
  38. 2026-08-12 03:51 UTCGHSA enrichment
  39. 2026-08-11 15:07 UTCEG score recompute
  40. 2026-08-11 15:07 UTCGHSA enrichment
  41. 2026-08-11 09:24 UTCEG score recompute
  42. 2026-08-11 09:24 UTCGHSA enrichment
  43. 2026-08-11 00:00 UTCEPSS rescore
  44. 2026-08-10 20:40 UTCGHSA enrichment
  45. 2026-08-10 07:56 UTCGHSA enrichment
  46. 2026-08-09 19:12 UTCEG score recompute
  47. 2026-08-09 19:12 UTCGHSA enrichment
  48. 2026-08-09 13:47 UTCEPSS rescore
  49. 2026-08-09 06:28 UTCGHSA enrichment
  50. 2026-08-08 17:44 UTCEG score recompute
  51. 2026-08-08 17:44 UTCGHSA enrichment
  52. 2026-08-08 16:37 UTCEPSS rescore
  53. 2026-08-08 04:59 UTCEG score recompute
  54. 2026-08-08 04:59 UTCGHSA enrichment
  55. 2026-08-07 16:15 UTCGHSA enrichment
  56. 2026-08-07 03:31 UTCGHSA enrichment
  57. 2026-08-06 14:47 UTCEG score recompute
  58. 2026-08-06 14:47 UTCGHSA enrichment
  59. 2026-08-06 13:47 UTCEPSS rescore
  60. 2026-08-06 01:58 UTCEG score recompute
  61. 2026-08-06 01:58 UTCGHSA enrichment
  62. 2026-08-05 19:17 UTCEPSS rescore
  63. 2026-08-05 19:17 UTCEPSS rescore
  64. 2026-08-05 13:14 UTCEG score recompute
  65. 2026-08-05 13:13 UTCGHSA enrichment
  66. 2026-08-05 05:57 UTCGHSA enrichment
  67. 2026-08-04 17:12 UTCEG score recompute
  68. 2026-08-04 17:12 UTCGHSA enrichment
  69. 2026-08-04 15:10 UTCEPSS rescore
  70. 2026-08-04 10:39 UTCEPSS rescore
  71. 2026-08-04 04:27 UTCGHSA enrichment
  72. 2026-08-03 15:43 UTCEG score recompute
  73. 2026-08-03 15:43 UTCGHSA enrichment
  74. 2026-08-03 10:36 UTCEPSS rescore
  75. 2026-08-03 02:59 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2026-64388?
CVE-2026-64388 is a high vulnerability published on July 25, 2026. In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgrp with SMB3 POSIX Extensions Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFSMOUNTCIFS_ACL or CIFSMOUNTMODEFROMSID were also…
When was CVE-2026-64388 disclosed?
CVE-2026-64388 was first published in the National Vulnerability Database on July 25, 2026, with the most recent update on August 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-64388 actively exploited?
CVE-2026-64388 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 97.9% of all scored CVEs.
What is the CVSS score of CVE-2026-64388?
CVE-2026-64388 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-64388?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-64388, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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