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Linux KernelOperating system · Linux

CVE-2026-53175

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-25
Fix available
A fix is available. Upgrade to 6.18.36 / 7.0.13 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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: inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and flushes every fragment queue that is not yet complete using inet_frag_queue_flush(). That helper frees all the skbs queued on the fragment queue but does not set INET_FRAG_COMPLETE, and leaves q->fragments_tail and q->last_run_head pointing at the freed skbs. The queue itself stays in the rhashtable. fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups, but it cannot stop a fragment that already obtained the queue through inet_frag_find() earlier and stalled just before taking the queue lock. Once that fragment resumes after the flush and takes the queue lock, it passes the INET_FRAG_COMPLETE check and then dereferences the freed fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of that pointer and, on the append path, writes ->next_frag, causing a slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly share the same flush path and are affected as well. Reset rb_fragments, fragments_tail and last_run_head in inet_frag_queue_flush() so a flushed queue no longer points at the freed skbs. A fragment that resumes after the flush and takes the queue lock then finds an empty queue and starts a new run instead of dereferencing the freed fragments_tail. ip_frag_reinit() already performed this reset after its own flush, so drop the now duplicate code there.

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 confidence

A use-after-free vulnerability in the Linux kernel's inet fragment queue handling allows a stalled fragment that obtained a queue before netns teardown to dereference freed skb pointers after fqdir_pre_exit() flushes incomplete fragment queues. The flush helper frees skbs but leaves q->fragments_tail and q->last_run_head pointing at freed memory, and doesn't set INET_FRAG_COMPLETE, allowing a racing fragment to pass the completion check and cause a UAF.

MitigationApply the kernel patch that resets rb_fragments, fragments_tail, and last_run_head in inet_frag_queue_flush() to prevent dereferencing freed skbs after flush. This is a kernel source code fix requiring recompilation.

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:>= 6.18.3, < 6.18.36>= 6.19.1, < 7.0.13= 6.12.93= 6.19= 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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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. Check the running kernel version
    Run `uname -r` or `cat /proc/version` to obtain the exact kernel version
    Affected if The version matches one of the affected ranges: >= 6.18.3 and < 6.18.36, >= 6.19.1 and < 7.0.13, equals 6.12.93, equals 6.19, or equals 7.1
  2. Identify if IP fragmentation is in use
    Check for active fragment queues by examining `/proc/net/ipv4/ipfrag` (IPv4) and `/proc/net/ipv6/ip6_frag` (IPv6), or run `lsmod | grep -E 'ip_frag|nf_defrag|frag'` to see loaded fragmentation-related modules
    Affected if Fragmentation is actively used (e.g., receiving fragmented packets, NAT/firewall rules processing fragments, or tunneled traffic) and the kernel version is in the affected range
  3. Examine kernel logs for inet_frag crashes
    Run `dmesg | grep -iE 'inet_frag|ip_frag|use.after|slab' ` and review `/var/log/kern.log` (if available) for any UAF or slab corruption messages related to fragmentation
    Affected if Kernel oops or crash messages reference inet_frag_queue_insert, INET_FRAG_COMPLETE, or dangling fragment pointers (fragments_tail, last_run_head)
  4. Check for netns teardown activity with fragments
    Monitor or review logs around network namespace destruction (docker/container deletion, vpn teardown, network namespace removal) for any associated crashes
    Affected if Crashes occur during or shortly after network namespace teardown operations while fragment processing was active

A system is affected if it runs a kernel version in the listed ranges and processes IP fragments, particularly in environments where network namespace teardown coincides with active fragmentation.

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 6.18.36 / 7.0.13 or later
Fixed in 6.18.367.0.13
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that resets rb_fragments, fragments_tail, and last_run_head in inet_frag_queue_flush() to prevent dereferencing freed skbs after flush. This is a kernel source code fix requiring recompilation.

Recommended fix High confidence

6.18.36+ / 6.19.1+ / 7.0.13+ / 6.12.94+ (depending on branch)

  1. Identify the currently running kernel version using `uname -r`
  2. If running 6.18.x (>= 6.18.3, < 6.18.36), upgrade to kernel 6.18.36 or later
  3. If running 6.19.x (>= 6.19.1, < 7.0.13), upgrade to kernel 7.0.13 or later
  4. If running exactly 6.19, upgrade to kernel 6.19.1 or later
  5. If running exactly 6.12.93, upgrade to kernel 6.12.94 or later (or a later stable branch)
  6. Reboot the system to apply the new kernel
  7. Verify the fix is applied by checking the kernel version after reboot
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with out-of-tree kernel modules or specific hardware drivers; test in staging before production deployment

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

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing16.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,360
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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-2026-53175 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
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  • Version or environment caveats, and links to real fixes
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