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Linux KernelOperating system · Linux

CVE-2026-52985

MEDIUM · 5.5 CVSS v3.1 Published 2026-06-24
Fix available
A fix is available. Upgrade to 5.10.258 / 5.15.209 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click 8 weeks old

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 · unedited
In the Linux kernel, the following vulnerability has been resolved: netdevsim: zero initialize struct iphdr in dummy sk_buff Syzbot reports a KMSAN uninit-value originating from nsim_dev_trap_skb_build, with the allocation also being performed in the same function. Fix this by calling skb_put_zero instead of skb_put to guarantee zero initialization of the whole IP header.

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 · moderate confidence

The netdevsim driver's nsim_dev_trap_skb_build function uses skb_put() to allocate memory for an IP header struct but fails to initialize it to zero, causing uninitialized kernel memory to be present in the sk_buff's iphdr structure. KMSAN detects this uninit-value bug. The fix is replacing skb_put with skb_put_zero to guarantee zero initialization of the entire IP header.

MitigationApply the one-line code change to use skb_put_zero instead of skb_put in nsim_dev_trap_skb_build, then rebuild and test the netdevsim kernel module to verify the KMSAN warning is resolved.

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
Affected:>= 5.4, < 5.10.258>= 5.11, < 5.15.209>= 5.16, < 6.1.175>= 6.2, < 6.6.141>= 6.7, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10= 7.1

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Confirm netdevsim driver is in use
    Check if the netdevsim kernel module is loaded: run 'lsmod | grep netdevsim' or check for netdevsim device nodes in /sys/devices/virtual/net/
    Affected if netdevsim module is loaded or netdevsim devices exist on the system
  2. Identify kernel version
    Run 'uname -r' to get the running kernel version and compare it against the affected ranges: >= 5.4 to < 5.10.258, >= 5.11 to < 5.15.209, >= 5.16 to < 6.1.175, >= 6.2 to < 6.6.141, >= 6.7 to < 6.12.91, >= 6.13 to < 6.18.33, >= 6.19 to < 7.0.10, or version 7.1
    Affected if The kernel version falls within any of the listed affected version ranges
  3. Locate vulnerable source code
    Find the netdevsim driver source file containing nsim_dev_trap_skb_build function, typically in drivers/net/ethernet/netdevsim/ in the kernel source tree, and search for the use of skb_put() when allocating the IP header
    Affected if The code uses skb_put() instead of skb_put_zero() for the iphdr structure allocation in nsim_dev_trap_skb_build
  4. Check for KMSAN warnings
    If running a kernel with KMSAN enabled (CONFIG_KMSAN), look for KMSAN uninit-value warnings in kernel logs (dmesg, journalctl) related to nsim_dev_trap_skb_build or netdevsim
    Affected if KMSAN reports an uninitialized value bug originating from the nsim_dev_trap_skb_build function when handling sk_buff iphdr data

You are affected if the netdevsim driver is loaded or used, your kernel version is within the affected ranges, and the vulnerable code pattern (skb_put without zero initialization) exists in your kernel source.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 5.10.258 / 5.15.209 / 6.1.175 or later
Fixed in 5.10.2585.15.2096.1.175
Interim mitigation

Apply the one-line code change to use skb_put_zero instead of skb_put in nsim_dev_trap_skb_build, then rebuild and test the netdevsim kernel module to verify the KMSAN warning is resolved.

Recommended fix High confidence

Linux Kernel 5.10.258, 5.15.209, 6.1.175, or 6.6.141 (or any subsequent version)

  1. Identify the file containing nsim_dev_trap_skb_build function in the netdevsim driver (typically in drivers/net/netdevsim/ directory)
  2. Locate the call to skb_put() that allocates memory for struct iphdr in that function
  3. Replace skb_put() with skb_put_zero() to ensure zero-initialization of the IP header structure
  4. Recompile the kernel with the updated netdevsim driver
Caveat Low risk - netdevsim is a testing/debug driver; the fix only changes memory initialization behavior

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,360
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52985 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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