CVE-2026-64388

HIGHPre-NVD 7.87.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

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, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-48932 (ENISA EUVD) · GHSA-p59x-f8qp-h8m2 (GitHub Security Advisories)Source: ENISA EUVD

7.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 7.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
7.8HIGHmedium confidence
EG Risk
35
EG Risk 35/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity78% × 45%
Impact severity (EG Severity): CVSS 7.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.1% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.1%
EPSS %ILE
2nd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.

EG Severity
7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.1% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

July 25, 2026

Last Modified

October 21, 2026

Advisory Details (2)

Auto-updated Jul 27, 2026
Patch available.
Web page

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
Web page

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.

Patch Availability(12)

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
linux5.10.103-1 ... 7.2~rc5-1~exp1 (500 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.1.106-1 ... 7.2~rc7-1~exp1 (358 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.100-1 ... 7.2~rc7-1~exp1 (181 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
linux6.12.100-1 ... 7.1~rc7-1~exp1 (159 versions)
  • every version up to 7.1.4-1: fixed in 7.1.4-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(12)

Data Freshness Timeline

(refreshed 14× in last 7d / 77× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 297 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 197 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  2. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  3. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  4. 2026-10-25 14:12 UTCEG score recompute
  5. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  6. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  7. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  8. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  9. 2026-10-21 13:50 UTCEG score recompute
  10. 2026-10-21 13:50 UTCVendor advisory
  11. 2026-10-21 13:50 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  12. 2026-10-21 12:56 UTCEG score recompute
  13. 2026-10-21 12:56 UTCVendor advisory
  14. 2026-10-21 12:56 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  15. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  16. 2026-10-19 21:40 UTCEG score recompute
  17. 2026-10-19 21:40 UTCVendor advisory
  18. 2026-10-19 21:40 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  19. 2026-10-19 20:44 UTCEG score recompute
  20. 2026-10-19 20:44 UTCVendor advisory
  21. 2026-10-19 20:44 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  22. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  23. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  24. 2026-10-18 03:22 UTCEG score recompute
  25. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
Show 75 more
  1. 2026-10-16 17:27 UTCEG score recompute
  2. 2026-10-16 17:27 UTCVendor advisory
  3. 2026-10-16 17:27 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  4. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  5. 2026-10-16 15:59 UTCEG score recompute
  6. 2026-10-16 15:59 UTCVendor advisory
  7. 2026-10-16 15:59 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  8. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  9. 2026-10-15 11:26 UTCEG score recompute
  10. 2026-10-15 11:26 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  11. 2026-10-15 10:31 UTCEG score recompute
  12. 2026-10-15 10:30 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  13. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  14. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  15. 2026-10-13 11:41 UTCEG score recompute
  16. 2026-10-13 11:41 UTCVendor advisory
  17. 2026-10-13 11:41 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  18. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  19. 2026-10-12 15:48 UTCEG score recompute
  20. 2026-10-11 19:32 UTCEG score recompute
  21. 2026-10-11 16:47 UTCEG score recompute
  22. 2026-10-11 14:09 UTCEG score recompute
  23. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  24. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  25. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  26. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  27. 2026-10-07 04:34 UTCEG score recompute
  28. 2026-10-07 04:34 UTCVendor advisory
  29. 2026-10-07 04:34 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  30. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  31. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  32. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  33. 2026-10-04 07:31 UTCEG score recompute
  34. 2026-10-04 07:31 UTCVendor advisory
  35. 2026-10-04 07:31 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  36. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  37. 2026-10-02 19:24 UTCEG score recompute
  38. 2026-10-02 19:24 UTCVendor advisory
  39. 2026-10-02 19:23 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  40. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  41. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  42. 2026-10-01 04:14 UTCEG score recompute
  43. 2026-10-01 04:14 UTCVendor advisory
  44. 2026-10-01 04:14 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  45. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  46. 2026-09-29 08:27 UTCEG score recompute
  47. 2026-09-29 08:27 UTCVendor advisory
  48. 2026-09-29 08:27 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  49. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  50. 2026-09-28 04:12 UTCEG score recompute
  51. 2026-09-28 04:12 UTCVendor advisory
  52. 2026-09-28 04:12 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  53. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  54. 2026-09-25 08:02 UTCEG score recompute
  55. 2026-09-25 08:02 UTCVendor advisory
  56. 2026-09-25 08:02 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  57. 2026-09-24 13:20 UTCVendor advisory
  58. 2026-09-24 13:20 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  59. 2026-09-24 00:35 UTCEG score recompute
  60. 2026-09-24 00:35 UTCVendor advisory
  61. 2026-09-24 00:35 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  62. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  63. 2026-09-23 10:55 UTCVendor advisory
  64. 2026-09-23 10:55 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  65. 2026-09-22 22:01 UTCEG score recompute
  66. 2026-09-22 22:01 UTCVendor advisory
  67. 2026-09-22 22:00 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  68. 2026-09-20 01:25 UTCVendor advisory
  69. 2026-09-20 01:25 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  70. 2026-09-18 19:47 UTCEG score recompute
  71. 2026-09-18 19:47 UTCVendor advisory
  72. 2026-09-18 19:47 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8
  73. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  74. 2026-09-18 02:46 UTCVendor advisory
  75. 2026-09-18 02:46 UTCGHSA enrichmentGHSA-p59x-f8qp-h8m2 · GitHub severity HIGH · GitHub CVSS 7.8

Frequently asked(5)

What is CVE-2026-64388?
CVE-2026-64388 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-64388 published?
The CVE record for CVE-2026-64388 was published on July 25, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 21, 2026; the record at its source may have been updated since.
Is CVE-2026-64388 actively exploited?
CVE-2026-64388 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (2nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-64388?
CVE-2026-64388 has a CVSS base score of 7.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-64388?
A fix for CVE-2026-64388 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-64388 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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