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NVD / CVE Program· CNA Linux

CVE-2026-72422: ksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE

Noroxi assessment

Priority: Monitor (action score 39/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.71% (FIRST EPSS); higher than 54% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 0c054227479ed7e36ebccb3a558bc0ef698264f6, 16a1ecf39c217e3d164bd32ef2a4f650abc067fa, 1c89da3baa2b1f269178afa87dc30479b8535776.

Low priority for now. Upgrade to Linux Linux 0c054227479ed7e36ebccb3a558bc0ef698264f6, 16a1ecf39c217e3d164bd32ef2a4f650abc067fa, 1c89da3baa2b1f269178afa87dc30479b8535776 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE conn->preauth_info is shared connection state (struct preauth_integrity_info, kmalloc-96) that is allocated and freed by the SMB2 NEGOTIATE handler and read by the response send path. smb2_handle_negotiate() allocates conn->preauth_info, and on a deassemble_neg_contexts() failure kfrees it and sets it to NULL. Both the allocation and the free/NULL happen under ksmbd_conn_lock(conn) (the connection srv_mutex), which is held across the whole handler body. The response send path smb3_preauth_hash_rsp(), called from the send: block of __handle_ksmbd_work(), reads conn->preauth_info and dereferences conn->preauth_info->Preauth_HashValue (via ksmbd_gen_preauth_integrity_hash()) without taking conn_lock. When a client drives two SMB2 NEGOTIATE requests on the same connection, one worker can free conn->preauth_info on the failing-negotiate path while a concurrent send-path worker is reading it, producing a slab use-after-free read (KASAN-confirmed). The send-path read tested conn->preauth_info for NULL but raced with the free that occurs between the NULL check and the dereference, so the NULL guard alone does not close the window. Serialize the NEGOTIATE-branch read in smb3_preauth_hash_rsp() under ksmbd_conn_lock(conn) and re-check conn->preauth_info inside the lock. Because the negotiate handler holds conn_lock across its kfree + NULL assignment, a reader that also takes conn_lock either runs fully before the allocation or fully after the NULL store, and can never observe the freed-but-not-yet-NULLed pointer. ksmbd_gen_preauth_integrity_hash() takes no locks itself (it only computes a SHA-512 over the buffer), so no lock-ordering inversion is introduced, and conn_lock is a sleepable mutex which is safe on this send path (it already performs network I/O).

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available
Published
Aug 15, 2026
Updated
Aug 17, 2026
EPSS
0.7% · 54th percentile
CWE
—

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.7%

CNA vs NVD score

NVD
—
CNA · Linux
9.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 8a8315a5960bd2b5ffc75f44fc089e57c3b17c44, ff20f1875889dbe4a67c9298e609d7c88cf6456d, 6.0affected
    • dd4e4c811898410e6a3ae3b63207b7c542860907 and later · before c7bef84740d1d57848c74f6f5b996606e43ea4feaffected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before d0a469122e7bf8338fec1949fb1e8e1290ed8caaaffected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before 7470511d085af1c7a043a60e53d52b512d5a10b1affected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before 16a1ecf39c217e3d164bd32ef2a4f650abc067faaffected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before 77bb0bbfcc4e777ca653174689e5e363f8ee63d1affected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before 1c89da3baa2b1f269178afa87dc30479b8535776affected · git
    • aa7253c2393f6dcd6a1468b0792f6da76edad917 and later · before 0c054227479ed7e36ebccb3a558bc0ef698264f6affected · git
    • 5.15.61 and later · before 5.15.212affected · semver
    • 5.18.18 and later · before 5.19affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.180-16.1.180-1
Debian:13linuxbefore 6.12.100-16.12.100-1
Debian:14linuxbefore 7.1.5-17.1.5-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-72414Aug 15, 2026 · net: dsa: sja1105: round up PTP perout pin duration
    0Monitor
  • ← EarlierCVE-2026-72417Aug 15, 2026 · netfilter: flowtable: Validate iph->ihl in nf_flow_ip4_tunnel_proto()
    39Monitor
  • Later →CVE-2026-72424Aug 15, 2026 · rtc: msc313: fix NULL deref in shared IRQ handler at probe
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0c054227479ed7e36ebccb3a558bc0ef698264f6Vendor (CNA)
Linux Linux16a1ecf39c217e3d164bd32ef2a4f650abc067faVendor (CNA)
Linux Linux1c89da3baa2b1f269178afa87dc30479b8535776Vendor (CNA)
Linux Linux5.15.212Vendor (CNA)
Linux Linux5.19Vendor (CNA)
Linux Linux5.20Vendor (CNA)
Linux Linux7470511d085af1c7a043a60e53d52b512d5a10b1Vendor (CNA)
Linux Linux77bb0bbfcc4e777ca653174689e5e363f8ee63d1Vendor (CNA)
Linux Linuxc7bef84740d1d57848c74f6f5b996606e43ea4feVendor (CNA)
Linux Linuxd0a469122e7bf8338fec1949fb1e8e1290ed8caaVendor (CNA)
debian:linux6.1.180-1 · Debian:12Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:02026-11-09

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+86 d
  3. TodayNov 10, 2026+87 d
EPSS, last 120 days+1% in 7 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturitynone → poc
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records