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NVD / CVE Program· CNA Linux

CVE-2026-89738: usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

Noroxi assessment

Priority: Monitor (action score 31/100)

  • 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: 0.19% (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 1674e34fe61ad3f5585dc833ba6bb6522912e6a5, 2440ce54b8c4c8aa6963c181eb56164a466fbe1c, 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1674e34fe61ad3f5585dc833ba6bb6522912e6a5, 2440ce54b8c4c8aa6963c181eb56164a466fbe1c, 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8 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: usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via mod_timer(). Both recover the same udc through container_of and dereference it on every iteration. Neither teardown path cancels this cycle. udc is devm-allocated, so it is freed after at91udc_remove() returns, and is likewise freed when probe fails and devres runs. A timer callback or work item that is pending or running at either point dereferences the freed udc. Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and from the usb_add_gadget_udc() failure path in probe; the remaining probe error paths fail before the timer is armed. timer_shutdown_sync() waits for a running callback and clears timer->function, which makes the work handler's mod_timer() a permanent no-op; cancel_work_sync() then drains any pending or running work whose re-arm attempt now does nothing. The timer must be shut down first, since cancelling the work alone would let the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and work_struct are never initialized. This does not require a fault; a normal driver unbind can interleave with an already queued work item. This issue was found by an in-house static analysis tool.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 8th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
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.

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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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Follow CVE-2026-89738

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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

    • 2.6.36affected
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before 2440ce54b8c4c8aa6963c181eb56164a466fbe1caffected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before 1674e34fe61ad3f5585dc833ba6bb6522912e6a5affected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before 723d73b245843d4fff4c3f42e857c78c2b2d414eaffected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before a2a602cb1e28d76a5398cec3fa21b0110385f501affected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8affected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before 557ef547d49ff5e6026a4d39bdd3113bd81d7688affected · git
    • 4037242c4f5ff77afe61bf07ca1e8a99490219e5 and later · before c27d13ce4bab80fbdf6523928071b6c24b37606caffected · git
    • before 2.6.36not affected · semver
    • 5.15.224 and later · up to and including 5.15.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.6-17.2.6-1

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
    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-2026-89736Sep 11, 2026 · usb: gadget: u_audio: Fix use-after-free on sound card disconnect
    31Monitor
  • ← EarlierCVE-2026-89737Sep 11, 2026 · usb: typec: thunderbolt: Disable work before freeing tbt on remove
    0Monitor
  • Later →CVE-2026-89739Sep 11, 2026 · usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition
    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 Linux1674e34fe61ad3f5585dc833ba6bb6522912e6a5Vendor (CNA)
Linux Linux2440ce54b8c4c8aa6963c181eb56164a466fbe1cVendor (CNA)
Linux Linux51a311eb97e91ce1aed3005cb71ccb2e30f8cce8Vendor (CNA)
Linux Linux557ef547d49ff5e6026a4d39bdd3113bd81d7688Vendor (CNA)
Linux Linux723d73b245843d4fff4c3f42e857c78c2b2d414eVendor (CNA)
Linux Linuxa2a602cb1e28d76a5398cec3fa21b0110385f501Vendor (CNA)
Linux Linuxc27d13ce4bab80fbdf6523928071b6c24b37606cVendor (CNA)
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.

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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.

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
high · data can be read
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
High
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: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.

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 (6 more)

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

All records