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CVE Record

CVE-2021-46956: virtiofs: fix memory leak in virtio_fs_probe()

In the Linux kernel, the following vulnerability has been resolved: virtiofs: fix memory leak in virtio_fs_probe() When accidentally passing twice the same tag to qemu, kmemleak ended up reporting a memory leak in virtiofs. Also, looking at the log I saw the following error (that's when I realised the duplicated tag): virtiofs: probe of virtio5 failed with error -17 Here's the kmemleak log for reference: unreferenced object 0xffff888103d47800 (size 1024): comm "systemd-udevd", pid 118, jiffies 4294893780 (age 18.340s) hex dump (first 32 bytes): 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N.......... ff ff ff ff ff ff ff ff 80 90 02 a0 ff ff ff ff ................ backtrace: [<000000000ebb87c1>] virtio_fs_probe+0x171/0x7ae [virtiofs] [<00000000f8aca419>] virtio_dev_probe+0x15f/0x210 [<000000004d6baf3c>] really_probe+0xea/0x430 [<00000000a6ceeac8>] device_driver_attach+0xa8/0xb0 [<00000000196f47a7>] __driver_attach+0x98/0x140 [<000000000b20601d>] bus_for_each_dev+0x7b/0xc0 [<00000000399c7b7f>] bus_add_driver+0x11b/0x1f0 [<0000000032b09ba7>] driver_register+0x8f/0xe0 [<00000000cdd55998>] 0xffffffffa002c013 [<000000000ea196a2>] do_one_initcall+0x64/0x2e0 [<0000000008f727ce>] do_init_module+0x5c/0x260 [<000000003cdedab6>] __do_sys_finit_module+0xb5/0x120 [<00000000ad2f48c6>] do_syscall_64+0x33/0x40 [<00000000809526b5>] entry_SYSCALL_64_after_hwframe+0x44/0xae

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel virtiofs memory leak triggered during device probing when QEMU is accidentally given duplicate virtiofs tags. The documented impact is leaked kernel memory and a failed virtiofs probe, not confirmed compromise or data theft.

Executive priority

Handle through normal kernel maintenance, with higher priority for virtualization platforms using virtiofs. Current public evidence supports operational reliability risk from memory leakage, not emergency breach response.

Technical view

The flaw is in virtio_fs_probe(). When duplicate virtiofs tags are presented, probing can fail with error -17 while memory allocated during probe is not freed. Kernel stable commits are referenced as the remediation evidence.

Likely exposure

Exposure is most likely in Linux virtualized environments using virtiofs with QEMU. The source bundle lists Linux kernel versions including 5.4, 5.4.118, 5.10.36, 5.11.20, 5.12.3, and 5.13 as affected evidence.

Exploitation context

No active exploitation is reported: KEV is false and the bundle provides no exploit-in-the-wild source. The described trigger is an accidental duplicate QEMU tag configuration that produced kmemleak output.

Researcher notes

The evidence is narrow: a kernel memory leak in virtiofs probe cleanup under duplicate-tag conditions. No CVSS, CWE, exploitability analysis, or attacker prerequisites are provided in the bundle, so severity should remain conservative.

Mitigation direction

  • Update affected Linux kernels using vendor or stable-kernel guidance.
  • Prioritize systems using virtiofs in QEMU-based virtualization.
  • Review QEMU virtiofs configuration for duplicate tags.
  • Track distribution advisories for backported fixes.
  • Avoid direct deploy assumptions; validate package-level fix status first.

Validation and detection

  • Inventory Linux kernel versions on virtiofs-capable virtualized systems.
  • Check whether virtiofs modules or devices are in use.
  • Review QEMU configuration for repeated virtiofs tags.
  • Confirm kernel package includes the referenced stable fix commits.
  • Monitor logs for virtiofs probe failures with error -17.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-46956 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxa62a8ef9d97da23762a588592c8b8eb50a8deb6a, a62a8ef9d97da23762a588592c8b8eb50a8deb6a, a62a8ef9d97da23762a588592c8b8eb50a8deb6a, a62a8ef9d97da23762a588592c8b8eb50a8deb6a, a62a8ef9d97da23762a588592c8b8eb50a8deb6aunaffected
LinuxLinux5.4, 0, 5.4.118, 5.10.36, 5.11.20, 5.12.3, 5.13affected
Weakness

CWE details

No CWE listed

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