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NVD / CVE Program· CNA Linux

CVE-2026-43185: ksmbd: fix signededness bug in smb_direct_prepare_negotiation()

CriticalCVSS 9.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 39/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.88% (FIRST EPSS); higher than 59.7% 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 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c, 55abc475d096da4a5356b6efb0cfdc6156bc1550, 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c, 55abc475d096da4a5356b6efb0cfdc6156bc1550, 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7 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 signededness bug in smb_direct_prepare_negotiation() smb_direct_prepare_negotiation() casts an unsigned __u32 value from sp->max_recv_size and req->preferred_send_size to a signed int before computing min_t(int, ...). A maliciously provided preferred_send_size of 0x80000000 will return as smaller than max_recv_size, and then be used to set the maximum allowed alowed receive size for the next message. By sending a second message with a large value (>1420 bytes) the attacker can then achieve a heap buffer overflow. This fix replaces min_t(int, ...) with min_t(u32)

Published
May 6, 2026
Updated
Nov 11, 2026
EPSS
0.8% · 59th percentile

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 · 0.8%

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.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Follow CVE-2026-43185

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • 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.

VendorProduct
linuxlinux kernel

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

    • 5.15affected
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06caffected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before a110dbe928561d440e9e117d17331139a0bedaceaffected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before ceae058eb707ddd0d68f0872f9d9f23b7c30c37baffected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 55abc475d096da4a5356b6efb0cfdc6156bc1550affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 6b4f875aac344cdd52a1f34cc70ed2f874a65757affected · git
    • before 5.15not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver
    • 6.6.160 and later · up to and including 6.6.*not affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.15 and later · before 6.18.16
  • linux linux kernel6.19 and later · before 6.19.6
  • linux linux kernel7.0

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-26.12.115-2
Debian:14linuxbefore 6.19.6-16.19.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-43183May 6, 2026 · media: cx25821: Fix a resource leak in cx25821_dev_setup()
    22Monitor
  • ← EarlierCVE-2026-43184May 6, 2026 · rnbd-srv: Zero the rsp buffer before using it
    30Monitor
  • Later →CVE-2026-43186May 6, 2026 · ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data()
    39Monitor

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 Linux1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06cVendor (CNA)
Linux Linux55abc475d096da4a5356b6efb0cfdc6156bc1550Vendor (CNA)
Linux Linux56eab82fa6fb5ca024b0514e249d40d9b23ee5a7Vendor (CNA)
Linux Linux6b4f875aac344cdd52a1f34cc70ed2f874a65757Vendor (CNA)
Linux Linuxa110dbe928561d440e9e117d17331139a0bedaceVendor (CNA)
Linux Linuxceae058eb707ddd0d68f0872f9d9f23b7c30c37bVendor (CNA)
debian:linux6.12.115-2 · Debian:13Package registry (OSV)
debian:linux6.19.6-1 · Debian:14Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

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.

No dated events beyond publication.

Variant candidates

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

  • CVE-2026-5320250 days apartaccel/ivpu: Fix signed integer truncation in IPC receive
    31Monitor
  • CVE-2026-5326750 days apartnetfilter: nft_ct: bail out on template ct in get eval
    31Monitor
  • CVE-2025-38459285 days apartatm: clip: Fix infinite recursive call of clip_push().
    31Monitor
  • CVE-2026-5339574 days apartnfsd: fix dead ACL conflict guard in nfsd4_create
    30Monitor
  • CVE-2026-4614922 days apartscsi: target: configfs: Bound snprintf() return in tg_pt_gp_members_show()
    28Monitor
  • CVE-2026-5332956 days apartdrm/amd/display: Use krealloc_array() in dal_vector_reserve()
    28Monitor

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

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)

CWE-674 · Uncontrolled Recursion

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.

ATT&CK techniques

—

References

Show all references (5 more)

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

All records