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CVE Record

CVE-2021-47024: vsock/virtio: free queued packets when closing socket

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: free queued packets when closing socket As reported by syzbot [1], there is a memory leak while closing the socket. We partially solved this issue with commit ac03046ece2b ("vsock/virtio: free packets during the socket release"), but we forgot to drain the RX queue when the socket is definitely closed by the scheduled work. To avoid future issues, let's use the new virtio_transport_remove_sock() to drain the RX queue before removing the socket from the af_vsock lists calling vsock_remove_sock(). [1] https://syzkaller.appspot.com/bug?extid=24452624fc4c571eedd9

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel memory-leak bug in virtio vsock socket shutdown. Affected systems may fail to free queued packets when a socket closes, wasting kernel memory. The sources do not provide a CVSS score or evidence of active exploitation, so urgency depends on whether affected Linux kernels and virtio/vsock are present.

Executive priority

Schedule remediation through normal kernel patching, with higher priority for virtualization platforms or workloads using virtio/vsock. There is no cited active exploitation or severity score, but kernel memory leaks can affect service reliability if reachable and repeated.

Technical view

The fix drains the virtio vsock receive queue before removing the socket from AF_VSOCK lists. The issue was reported by syzbot and partially addressed earlier, but queued RX packets could remain during final socket close. Public references are Linux stable commits; no exploit details are provided.

Likely exposure

Exposure is most likely on Linux systems running affected kernel versions with virtio/vsock functionality present. The source lists Linux as affected and includes 5.2 through later 5.10, 5.11, 5.12, and 5.13-era versions, but distro backports must be checked.

Exploitation context

The provided sources only describe a memory leak during socket close and a syzbot report. They do not show active exploitation, KEV listing, exploit availability, privilege requirements, or remote reachability. Treat this primarily as a potential kernel resource-exhaustion issue until vendor guidance says otherwise.

Researcher notes

Key uncertainty is reachability. The public record identifies the vulnerable close path and stable fixes, but not attacker prerequisites or impact rating. Focus validation on kernel lineage, backport status, and whether virtio vsock paths are exposed in the local virtualization model.

Mitigation direction

  • Update to a vendor-supported kernel containing the referenced stable fixes.
  • Check distribution advisories for backported fixes rather than relying only on version numbers.
  • Prioritize hosts where virtio/vsock is enabled or used by virtualization workloads.
  • Monitor kernel memory pressure until patched.
  • If patching is delayed, ask the vendor about supported exposure-reduction options.

Validation and detection

  • Inventory Linux kernel versions across servers, images, and virtualized workloads.
  • Confirm whether virtio/vsock support is enabled or loaded on affected systems.
  • Verify vendor packages include the relevant stable kernel fix or backport.
  • Review change management records for kernels based on affected 5.x releases.
  • Track unresolved systems separately where kernel provenance is unclear.
Prepared
Confidence
medium
Sources
6

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2021-47024 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
5Source 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
LinuxLinuxac03046ece2b158ebd204dfc4896fd9f39f0e6c8, ac03046ece2b158ebd204dfc4896fd9f39f0e6c8, ac03046ece2b158ebd204dfc4896fd9f39f0e6c8, ac03046ece2b158ebd204dfc4896fd9f39f0e6c8, 4ea082cd3c400cd5bb36a7beb7e441bf3e29350d, 4e539fa2dec4db3405e47002f2878aa4a99eb68b, 4af8a327aeba102aaa9b78f3451f725bc590b237, 51adb8ebe8c1d80528fc2ea863cfea9d32d2c52b, 7d29c9ad0ed525c1b10e29cfca4fb1eece1e93fbunaffected
LinuxLinux5.2, 0, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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