NVD / CVE Program· CNA Linux

CVE-2026-68173: ublk: wait on ublk_dev_ready() instead of ub->completion

Noroxi assessment

Priority: Monitor (action score 28/100)

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: 0.16% (FIRST EPSS).
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 432a9b2780c0a01caf547bd1fc2fcf28aeb8d173, 6.15, 7dd26adf7e7d482af524e3a0cca4a81ef7c159d0.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 432a9b2780c0a01caf547bd1fc2fcf28aeb8d173, 6.15, 7dd26adf7e7d482af524e3a0cca4a81ef7c159d0 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: ublk: wait on ublk_dev_ready() instead of ub->completion ub->completion is only re-armed by a successful START_USER_RECOVERY. If the ublk server sends END_USER_RECOVERY without one - e.g. its START failed with -EBUSY and the error was ignored - the wait is satisfied by the stale completion of the previous recovery cycle, and the device is marked LIVE and the requeue list kicked while the FETCH stream is still running and ubq->canceling is still set. The kick redispatches a previously requeued request, __ublk_queue_rq_common() sees ->canceling and parks it again via __ublk_abort_rq(), and after the last FETCH clears ->canceling nothing ever kicks the requeue list again: the request is stranded there while holding its tag. If it is the flush machinery's flush_rq, every subsequent fsync piles up in uninterruptible sleep and teardown hangs on tag draining. This matches a report of a lost PREFLUSH with ext4 on top of ublk after daemon crash recovery. ub->completion is an edge-triggered latch used as a proxy for the level condition "every queue has fetched all I/O commands", which can regress (F_BATCH's UNPREP, daemon death) and whose re-arm can be skipped. Drop it and wait on the real condition instead: the new helper ublk_wait_dev_ready_and_lock() waits on ublk_dev_ready() via wait_var_event_interruptible(), woken from ublk_mark_io_ready(), then re-checks it under ub->mutex, waiting again on regression, and returns with the mutex held and readiness guaranteed. Readiness becomes true in the same ub->mutex critical section that clears the last queue's ->canceling, so END_USER_RECOVERY marks the device LIVE and kicks the requeue list strictly after ->canceling clears. The wait stays interruptible, so a server whose daemon died can still be signalled out. For ublk_ctrl_start_dev() this replaces the fail-fast -EINVAL on an F_BATCH ready->UNPREP regression with waiting until the device is ready again.

HighCVSS 7.1 · v3.1—No exploit Fix available

Published: Aug 10, 2026
Updated: Aug 17, 2026
EPSS: 0.1% · 5th percentile
CWE: —

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 28 / 40 · 7.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.1%

CNA vs NVD score

NVD: —
CNA · Linux: 7.1; 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
No public exploit code on record
A fix has been released

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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.

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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
- 42ea64e01c96e594fb4f80c54dfe4f934d008a6e, 6.15affected
- 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b and later · before 7dd26adf7e7d482af524e3a0cca4a81ef7c159d0affected · git
- 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b and later · before 8f188dd11a1c2ad94caeaee36ef68bb8221d4a12affected · git
- 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b and later · before 432a9b2780c0a01caf547bd1fc2fcf28aeb8d173affected · git
- 6.14.6 and later · before 6.15affected · semver
- before 6.15not affected · semver
- 6.18.42 and later · up to and including 6.18.*not affected · semver
- 7.1.6 and later · up to and including 7.1.*not affected · semver
- 7.2 and laternot affected · original_commit_for_fix

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Debian:14	linux	before 7.1.6-1	7.1.6-1

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
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CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
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CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
40Plan

Published before and after this one in the same product

← EarlierCVE-2026-68170Aug 10, 2026 · mptcp: fix stale skb->sk reference on subflow close
39Monitor
← EarlierCVE-2026-68172Aug 10, 2026 · arm64: make huge_ptep_get handled unaligned addresses
28Monitor
Later →CVE-2026-68174Aug 10, 2026 · tracing: Fix union collision of module and refcnt for dynamic events
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 / package	Fixed version	Source
Linux Linux	432a9b2780c0a01caf547bd1fc2fcf28aeb8d173	Vendor (CNA)
Linux Linux	6.15	Vendor (CNA)
Linux Linux	7dd26adf7e7d482af524e3a0cca4a81ef7c159d0	Vendor (CNA)
Linux Linux	8f188dd11a1c2ad94caeaee36ef68bb8221d4a12	Vendor (CNA)
debian:linux	7.1.6-1 · Debian:14	Package 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.

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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.

TR-26-0800 · Aug 11, 2026(Linux Kernel Güvenlik Bildirimi)

All national notices →

Technical details

Attack conditions

Someone with local access to the system can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: High
Availability impact: High

Weakness class (CWE)

—

CVSS vector

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

Fix✗ → ✓Sep 28, 2026, 10:08 PM UTC

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

References

git.kernel.org/stable/c/432a9b2780c0a01caf547bd1fc2fcf28aeb8d173

Show all references (2 more)

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

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