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NVD / CVE Program· CNA Linux

CVE-2026-31478: ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()

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: 0.50% (FIRST EPSS).
  • 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.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 0e55f63dd08f09651d39e1b709a91705a8a0ddcb, 4cb537ae4f37d7d0f617815ed4bed7173fb50861, 5.15.203.

Low priority for now. Upgrade to Linux Linux 0e55f63dd08f09651d39e1b709a91705a8a0ddcb, 4cb537ae4f37d7d0f617815ed4bed7173fb50861, 5.15.203 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: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len() After this commit (e2b76ab8b5c9 "ksmbd: add support for read compound"), response buffer management was changed to use dynamic iov array. In the new design, smb2_calc_max_out_buf_len() expects the second argument (hdr2_len) to be the offset of ->Buffer field in the response structure, not a hardcoded magic number. Fix the remaining call sites to use the correct offsetof() value.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Apr 22, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 43th 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 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

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

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-31478

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

Affected versions

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

  • linux linux kernel5.15.145 and later · before 5.15.203
  • linux linux kernel6.1.71 and later · before 6.1.168
  • linux linux kernel6.6.1 and later · before 6.6.131
  • linux linux kernel6.7 and later · before 6.12.80
  • linux linux kernel6.13 and later · before 6.18.21
  • linux linux kernel6.19 and later · before 6.19.11
  • linux linux kernel6.6
  • linux linux kernel7.0

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

    • 6.6affected
    • f2283680a80571ca82d710bc6ecd8f8beac67d63 and later · before 70b4c414889492c522b6e4331562360f49be2361affected · git
    • 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 and later · before 9a7166f0ef8cbb7bb48dd05e2471d995566003f5affected · git
    • e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d and later · before c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683affected · git
    • e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d and later · before 6aef1765d6807e0f027cd87f6ac973eb0879a46daffected · git
    • e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d and later · before 80824c7e527b70cf9039534e60aff592e8f209d1affected · git
    • e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d and later · before 4cb537ae4f37d7d0f617815ed4bed7173fb50861affected · git
    • e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d and later · before 0e55f63dd08f09651d39e1b709a91705a8a0ddcbaffected · git
    • 5.15.145 and later · before 5.15.203affected · semver
    • 6.1.71 and later · before 6.1.168affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.11-16.19.11-1

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-2026-31473Apr 22, 2026 · media: mc, v4l2: serialize REINIT and REQBUFS with req_queue_mutex
    31Monitor
  • ← EarlierCVE-2026-31474Apr 22, 2026 · can: isotp: fix tx.buf use-after-free in isotp_sendmsg()
    31Monitor
  • Later →CVE-2026-31479Apr 22, 2026 · drm/xe: always keep track of remap prev/next
    31Monitor

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 Linux0e55f63dd08f09651d39e1b709a91705a8a0ddcbVendor (CNA)
Linux Linux4cb537ae4f37d7d0f617815ed4bed7173fb50861Vendor (CNA)
Linux Linux5.15.203Vendor (CNA)
Linux Linux6.1.168Vendor (CNA)
Linux Linux6aef1765d6807e0f027cd87f6ac973eb0879a46dVendor (CNA)
Linux Linux70b4c414889492c522b6e4331562360f49be2361Vendor (CNA)
Linux Linux80824c7e527b70cf9039534e60aff592e8f209d1Vendor (CNA)
Linux Linux9a7166f0ef8cbb7bb48dd05e2471d995566003f5Vendor (CNA)
Linux Linuxc3a89e3ec1ccf64fa6a34e391e1581ebbcba8683Vendor (CNA)
debian:linux6.1.170-1 · Debian:12Package 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.

No history yet (it accumulates with the daily EPSS job).

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.

  • CVE-2026-5309163 days apartnet: pull headers in qdisc_pkt_len_segs_init()
    33Monitor
  • CVE-2026-5336685 days apartipv4: account for fraggap on the paged allocation path
    31Monitor
  • CVE-2026-6403988 days apartdrm/msm/snapshot: fix dumping of the unaligned regions
    30Monitor
  • CVE-2025-7128614 days apartASoC: SOF: ipc4-topology: Correct the allocation size for bytes controls
    22Monitor
  • CVE-2026-4310714 days apartxfrm: account XFRMA_IF_ID in aevent size calculation
    22Monitor
  • CVE-2026-4330216 days apartdrm/v3d: Set DMA segment size to avoid debug warnings
    22Monitor

Chain candidates

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

—

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)

CWE-131 · Incorrect Calculation of Buffer Size

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

—

Change log

  1. SSVC exploitation— → none
  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