VulnerabilityPublished 25 Sep 2026Updated 5 Oct 2026

CVE-2026-97563: Linux kernel · smb: client: reject out-of-bounds DataOffset in CIFSSMBRead()

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-97563· High

Not known to be exploited.

Data as of 26 Oct 2026, 13:47 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade to a Linux kernel version that includes the patch validating DataOffset and DataLength in CIFSSMBRead(). Avoid using SMB1 protocol by default, as it is not negotiated automatically. If SMB1 must be used, ensure the kernel is updated to a version with this fix applied. Patch status is not explicitly stated; check vendor advisories for the specific kernel versions containing the fix.

Description

A vulnerability in the Linux kernel SMB1 client allows a malicious or compromised SMB1 server to cause out-of-bounds reads in the CIFSSMBRead() function by providing a crafted DataOffset value. This can lead to information disclosure or denial of service. The issue arises because DataOffset is not validated against the response length, allowing memcpy() to read beyond the buffer. SMB1 is not negotiated by default, requiring explicit use of vers=1.0 mount to reach the vulnerable code. The vulnerability has been resolved by adding proper validation to ensure DataOffset and DataLength fit within the response buffer.

Impact

An attacker controlling or impersonating an SMB1 server can cause the Linux kernel SMB1 client to read out-of-bounds kernel memory, potentially leaking sensitive information or causing a kernel crash leading to denial of service. Since SMB1 is not negotiated by default, exploitation requires explicit SMB1 usage, reducing exposure. No known exploits in the wild have been reported.

Summary

The Linux kernel SMB1 synchronous read helper CIFSSMBRead() previously validated DataLength but did not validate DataOffset, which is used to calculate the source pointer for memcpy(). A malicious SMB1 server can send a response with a valid DataLength but a large DataOffset, causing memcpy() to read beyond the response buffer. This results in disclosure of kernel heap memory or a kernel crash (denial of service). The fix adds overflow-safe validation to reject responses where DataOffset + DataLength exceeds the response length. SMB1 is not negotiated by default, so exploitation requires explicit SMB1 mount.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-97563
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:Pro:14.04:LTS, Ubuntu:Pro:16.04:LTS, Ubuntu:16.04:LTS, Ubuntu:Pro:FIPS:16.04:LTS, Ubuntu:Pro:18.04:LTS, Ubuntu:18.04:LTS, Ubuntu:Pro:FIPS-updates:18.04:LTS, Ubuntu:Pro:FIPS:18.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:FIPS-updates:20.04:LTS, Ubuntu:Pro:FIPS:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:26.04:LTS

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 16:35 UTC

Technical details

References

Community reviews

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