CVE-2026-89637

CRITICALPre-NVD 9.89.8
EchelonGraph scoreMEDIUM confidence

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

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-09-11. A secondary CVSS source baseline 9.8; 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
9.8EG
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: 0.6%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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

smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2

When a valid primary TRANSACT2 response has been received (mid->resp_buf set, mid->multiRsp true) and a subsequent secondary response causes cifs_check_trans2() to return false -- either because the SMB header is invalid (malformed != 0) or because check2ndT2() rejects the PDU -- handle_mid() overwrites mid->resp_buf with the new buffer (leaking the primary buffer) and, because mid->multiRsp is set, skips the server->smallbuf/bigbuf NULL-out. When the user thread frees mid->resp_buf, server->smallbuf or server->bigbuf is left dangling; the demux thread reuses it for the next packet, resulting in a use-after-free.

Combine both early-exit conditions and, when mid->multiRsp is already set, abort the pending transaction inline: set multiEnd, call dequeue_mid() with malformed=true, and return true so handle_mid() exits without touching mid->resp_buf or the server buffer pointers.

CVSS v3
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
44
EG Risk 44/100

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 (value × EchelonGraph’s weight)
Severity98% × 45%
The EG Score, 9.8 of 10.
Exploitation0.6% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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
0.6%
EPSS %ILE
46th
KEV
Not listed

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 (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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

September 11, 2026

Last Modified

September 13, 2026

Advisory Details (3)

Auto-updated Oct 11, 2026
Patch available.
Web page

smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2 - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/9eed72e9534b10a6d9f8f5146feff3db53aebdba
Web page

smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2 - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/730d0bb19507b9e19c2fe5343109ac618e2fbce5
Web page

smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2 - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5e6533a683f6a851158d9f33fb4ea8f4f25d7f84

Vendor Advisories for CVE-2026-89637(1)

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

Affected Packages

(3 across 3 ecosystems)
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 ... 7.2~rc7-1~exp1 (178 versions)
  • every version up to 7.2.6-1: fixed in 7.2.6-1
—

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 66× in last 7d / 356× 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 374 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 274 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 09:57 UTCEG score recompute
  2. 2026-10-14 09:57 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  4. 2026-10-13 08:02 UTCEG score recompute
  5. 2026-10-13 08:02 UTCVendor advisory
  6. 2026-10-13 08:02 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  7. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  8. 2026-10-12 14:48 UTCEG score recompute
  9. 2026-10-12 09:06 UTCEG score recompute
  10. 2026-10-12 09:06 UTCVendor advisory
  11. 2026-10-12 09:05 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-11 21:06 UTCVendor advisory
  13. 2026-10-11 21:06 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  14. 2026-10-11 19:15 UTCEG score recompute
  15. 2026-10-11 16:31 UTCEG score recompute
  16. 2026-10-11 15:51 UTCEG score recompute
  17. 2026-10-11 15:51 UTCVendor advisory
  18. 2026-10-11 15:51 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  19. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  20. 2026-10-11 13:47 UTCEG score recompute
  21. 2026-10-11 11:40 UTCEG score recompute
  22. 2026-10-11 11:40 UTCVendor advisory
  23. 2026-10-11 11:40 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  24. 2026-10-11 06:50 UTCVendor advisory
  25. 2026-10-11 06:50 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
Show 75 more
  1. 2026-10-10 23:07 UTCEG score recompute
  2. 2026-10-10 23:07 UTCVendor advisory
  3. 2026-10-10 23:07 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  4. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  5. 2026-10-10 17:53 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-10 13:29 UTCVendor advisory
  7. 2026-10-10 13:29 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  8. 2026-10-10 09:17 UTCVendor advisory
  9. 2026-10-10 09:17 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  10. 2026-10-10 05:05 UTCVendor advisory
  11. 2026-10-10 05:04 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-10 00:54 UTCVendor advisory
  13. 2026-10-10 00:54 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  14. 2026-10-09 20:43 UTCEG score recompute
  15. 2026-10-09 20:43 UTCVendor advisory
  16. 2026-10-09 20:43 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  17. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  18. 2026-10-09 16:31 UTCVendor advisory
  19. 2026-10-09 16:31 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  20. 2026-10-09 07:36 UTCVendor advisory
  21. 2026-10-09 07:36 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  22. 2026-10-09 03:24 UTCVendor advisory
  23. 2026-10-09 03:24 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  24. 2026-10-08 23:14 UTCEG score recompute
  25. 2026-10-08 23:14 UTCVendor advisory
  26. 2026-10-08 23:14 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  27. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  28. 2026-10-08 12:34 UTCVendor advisory
  29. 2026-10-08 12:34 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  30. 2026-10-08 08:16 UTCVendor advisory
  31. 2026-10-08 08:16 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  32. 2026-10-08 04:04 UTCVendor advisory
  33. 2026-10-08 04:04 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  34. 2026-10-07 23:53 UTCEG score recompute
  35. 2026-10-07 23:53 UTCVendor advisory
  36. 2026-10-07 23:53 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  37. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  38. 2026-10-07 19:41 UTCVendor advisory
  39. 2026-10-07 19:41 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  40. 2026-10-07 12:56 UTCVendor advisory
  41. 2026-10-07 12:56 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  42. 2026-10-07 08:39 UTCVendor advisory
  43. 2026-10-07 08:39 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  44. 2026-10-07 04:28 UTCVendor advisory
  45. 2026-10-07 04:28 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  46. 2026-10-07 00:17 UTCVendor advisory
  47. 2026-10-07 00:17 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  48. 2026-10-06 20:06 UTCVendor advisory
  49. 2026-10-06 20:06 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  50. 2026-10-06 15:46 UTCEG score recompute
  51. 2026-10-06 15:46 UTCVendor advisory
  52. 2026-10-06 15:46 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  53. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  54. 2026-10-06 11:21 UTCVendor advisory
  55. 2026-10-06 11:21 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  56. 2026-10-06 07:10 UTCVendor advisory
  57. 2026-10-06 07:10 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  58. 2026-10-06 02:39 UTCVendor advisory
  59. 2026-10-06 02:39 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  60. 2026-10-05 22:28 UTCVendor advisory
  61. 2026-10-05 22:28 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  62. 2026-10-05 18:10 UTCEG score recompute
  63. 2026-10-05 18:10 UTCVendor advisory
  64. 2026-10-05 18:09 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  65. 2026-10-05 17:44 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  66. 2026-10-05 13:58 UTCVendor advisory
  67. 2026-10-05 13:58 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  68. 2026-10-05 09:47 UTCVendor advisory
  69. 2026-10-05 09:47 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  70. 2026-10-05 05:36 UTCVendor advisory
  71. 2026-10-05 05:36 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  72. 2026-10-05 01:25 UTCEG score recompute
  73. 2026-10-05 01:25 UTCVendor advisory
  74. 2026-10-05 01:25 UTCGHSA enrichmentGHSA-q27p-5553-xhrr · GitHub severity CRITICAL · GitHub CVSS 9.8
  75. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.6% · 48th percentile

Frequently asked(5)

What is CVE-2026-89637?
CVE-2026-89637 is a critical-severity vulnerability; its CVE record was published on September 11, 2026. In the Linux kernel, the following vulnerability has been resolved: smb: client: fix UAF and buffer leak in cifschecktrans2() for malformed secondary T2 When a valid primary TRANSACT2 response has been received (mid->resp_buf set, mid->multiRsp true) and a subsequent secondary response causes…
When was the CVE record for CVE-2026-89637 published?
The CVE record for CVE-2026-89637 was published on September 11, 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 September 13, 2026; the record at its source may have been updated since.
Is CVE-2026-89637 actively exploited?
CVE-2026-89637 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (46th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-89637?
CVE-2026-89637 has a CVSS base score of 9.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-89637?
A fix for CVE-2026-89637 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-89637 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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