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NVD / CVE Program· CNA Linux

CVE-2026-97557: smb: client: avoid leaking refcount in cifs_queue_oplock_break()

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.66% (FIRST EPSS); higher than 51.7% 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 0fb92ac85db58945ad7b970ff17674001487b3a3, 13b9519b19e6e58a6cd01e63062cd1da7bd6449a, 2ed2c29dd9593637cfa25ac1eb23241b20202778; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.158.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0fb92ac85db58945ad7b970ff17674001487b3a3, 13b9519b19e6e58a6cd01e63062cd1da7bd6449a, 2ed2c29dd9593637cfa25ac1eb23241b20202778; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.158.1-1 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: smb: client: avoid leaking refcount in cifs_queue_oplock_break() cifs_queue_oplock_break() unconditionally takes a reference on the target file before queueing cifs_oplock_break(). Only that work item decreases the reference counter again. If another oplock break arrives while that work is still queued, queue_work() will return false and not queue this second work item. As a result, we will never reach the point to drop the file reference again and are leaking this reference. This can be triggered when interacting with a slow-responding server. As a result, later unmount operations for this file system will fail with BUG: Dentry ... still in use (1) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) kernel BUG at fs/super.c:777! Fix this by only incrementing the reference count if the work has been queued successfully. Taking it after queue_work() is safe because all three callers hold tcon->open_file_lock across the call and _cifsFileInfo_put() decrements under that same lock, so a worker that starts the handler in the window cannot drop the reference before it has been taken.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Sep 25, 2026
Updated
Oct 30, 2026
EPSS
0.6% · 51th percentile
CWE
—

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CNA vs NVD score

NVD
—
CNA · Linux
7.5
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-2026-97557

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?

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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

    • 2429fcf06d3cb962693868ab0a927c9038f12a2d, 1ee4f2d7cdcd4508cc3cbe3b2622d7177b89da12, 53fc31a4853e30d6e8f142b824f724da27ff3e40, 8092ecc306d81186a64cda42411121f4d35aaff4, ebac4d0adf68f8962bd82fcf483936edd6ec095b, 5.1affected
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before 13b9519b19e6e58a6cd01e63062cd1da7bd6449aaffected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before 0fb92ac85db58945ad7b970ff17674001487b3a3affected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before 735a3a610136ae10f381d0909dff38e5b5c5f056affected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before de2a6bcff2659bea40c7485115b57f0ae189fc01affected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before af0193bbf1ac8c0f67f972998b0cc629d6116cf6affected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before 2ed2c29dd9593637cfa25ac1eb23241b20202778affected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before dfe7b750c7e069873a8a57a11c816831a235618aaffected · git
    • b98749cac4a695f084a5ff076f4510b23e353ecd and later · before 9f2e63f1b2d5fc5b5423424902c091123e220e7eaffected · git
    • 3.16.72 and later · before 3.17affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.7-17.2.7-1

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-2026-97555Sep 25, 2026 · smb: client: fix heap overflow in DACL owner/group rewrite
    35Monitor
  • ← EarlierCVE-2026-97556Sep 25, 2026 · smb: client: avoid leaking refcount when cifs_sb_tlink() fails
    0Monitor
  • Later →CVE-2026-97558Sep 25, 2026 · smb: client: fix cifsFileInfo reference leak in deferred close
    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 Linux0fb92ac85db58945ad7b970ff17674001487b3a3Vendor (CNA)
Linux Linux13b9519b19e6e58a6cd01e63062cd1da7bd6449aVendor (CNA)
Linux Linux2ed2c29dd9593637cfa25ac1eb23241b20202778Vendor (CNA)
Linux Linux3.17Vendor (CNA)
Linux Linux4.10Vendor (CNA)
Linux Linux4.15Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux5.1Vendor (CNA)
Linux Linux735a3a610136ae10f381d0909dff38e5b5c5f056Vendor (CNA)
Linux Linux9f2e63f1b2d5fc5b5423424902c091123e220e7eVendor (CNA)
Linux Linuxaf0193bbf1ac8c0f67f972998b0cc629d6116cf6Vendor (CNA)
Linux Linuxde2a6bcff2659bea40c7485115b57f0ae189fc01Vendor (CNA)
Linux Linuxdfe7b750c7e069873a8a57a11c816831a235618aVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.06.6.158.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · 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.

EPSS, last 120 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.

—

Bug bounty scope

No known public program.

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

National notice (Türkiye Cybersecurity Directorate / USOM)

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

All national notices →

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

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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. Fix✗ → ✓

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

References

Show all references (7 more)

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

All records