Linux KernelOperating system · Linux
CVE-2026-53365
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix zerocopy completion for multi-skb sends When a large message is fragmented into multiple skbs, the zerocopy uarg is only allocated and attached to the last skb in the loop. Non-final skbs carry pinned user pages with no completion tracking, so the kernel has no way to notify userspace when those pages are safe to reuse. If the loop breaks early the uarg is never allocated at all, leaking pinned pages with no completion notification. Fix this by following the approach used by TCP: allocate the zerocopy uarg (if not provided by the caller) before the send loop and attach it to every skb via skb_zcopy_set(), which takes a reference per skb. Each skb's completion properly decrements the refcount, and the notification only fires after the last skb is freed. On failure, if no data was sent, the uarg is cleanly aborted via net_zcopy_put_abort(). This issue was initially discovered by sashiko while reviewing commit 1cb36e252211 ("vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting") but was pre-existing.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Linux kernel's vsock/virtio implementation, when a large message is fragmented into multiple skbs, the zerocopy user argument is incorrectly allocated only for the last skb. Non-final skbs carry pinned user pages without completion tracking, preventing the kernel from notifying userspace when pages are safe to reuse. If the send loop terminates early, pages are leaked with no notification. The fix allocates the uarg before the send loop and attaches it to every skb via skb_zcopy_set() with reference counting, ensuring proper cleanup and notification.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 6.7, < 6.18.34>= 6.19, < 7.0.11= 7.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check your kernel versionRun `uname -r` to get the running kernel versionAffected if The version is >= 6.7 and < 6.18.34, OR >= 6.19 and < 7.0.11, OR exactly 7.1
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Verify vsock/virtio module availabilityRun `lsmod | grep virtio` or check for /dev/vsock in the filesystemAffected if The virtio_vsock module is loaded or /dev/vsock exists, indicating vsock support is present
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Identify active vsock connections with zerocopyCheck /proc/net/protocols or use `ss -vsock` if available to see active vsock connections; look for SO_ZEROCOPY or MSG_ZEROCOPY usage in socket statsAffected if There are active vsock connections using zerocopy (SO_ZEROCOPY flag enabled)
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Check for large message transfers that may fragmentMonitor network statistics via `/proc/net/snmp` or use `netstat -vsock` to identify large message transfers; the flaw triggers when messages are larger than typical MTU and fragment across multiple skbsAffected if Large vsock messages are being transmitted (typically >64KB) which would cause fragmentation into multiple skbs
You are affected if your kernel version falls in the vulnerable range AND you are actively using vsock/virtio with zerocopy enabled for large message transfers that fragment into multiple skbs.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped6.18.347.0.11
This is a kernel-side fix requiring update to a patched Linux kernel version. Users of vsock/virtio with zerocopy should monitor kernel updates. The vulnerability could lead to pinned page exhaustion (DoS) if actively exploited with large multi-skb messages.
6.18.34+ (6.18.y), 7.0.11+ (7.0.y), or 7.2+ (7.1.y)
- Upgrade the Linux kernel to version 6.18.34 or later if using the 6.18.y stable branch
- Alternatively, upgrade to version 7.0.11 or later if using the 7.0.y stable branch
- Alternatively, upgrade to version 7.2 or later if currently on the 7.1.y branch
- After kernel upgrade, reboot the system to load the fixed kernel version
- Verify the fix is applied by checking the kernel version: `uname -r`
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing5.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-53365 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-53365 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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