Linux KernelOperating system · Linux
CVE-2026-52998
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: netfilter: nfnetlink_osf: fix potential NULL dereference in ttl check The nf_osf_ttl() function accessed skb->dev to perform a local interface address lookup without verifying that the device pointer was valid. Additionally, the implementation utilized an in_dev_for_each_ifa_rcu loop to match the packet source address against local interface addresses. It assumed that packets from the same subnet should not see a decrement on the initial TTL. A packet might appear it is from the same subnet but it actually isn't especially in modern environments with containers and virtual switching. Remove the device dereference and interface loop. Replace the logic with a switch statement that evaluates the TTL according to the ttl_check.
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 confidenceThe nf_osf_ttl() function in the Linux kernel's netfilter OS fingerprinting module dereferences skb->dev without validating the device pointer is non-NULL, leading to a potential NULL dereference. Additionally, the function incorrectly assumes packets from the same subnet shouldn't see TTL decrements, which fails in containerized and virtual switching environments where such assumptions are invalid.
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
>= 2.6.31, < 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, < 7.0.10CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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.
-
Check kernel version against affected rangesRun `uname -r` or `cat /proc/version` to get the kernel version. Compare against: >= 2.6.31, < 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, < 7.0.10Affected if The installed kernel version falls within any of the affected ranges listed above
-
Verify if netfilter OS fingerprinting module is activeCheck if the nf_osf module is loaded: `lsmod | grep osf` or check if it's built into the kernel config: `cat /boot/config-$(uname -r) | grep CONFIG_NETFILTER_XT_TARGET_OSF`Affected if The nf_osf module is loaded or built into the kernel and OS fingerprinting is being used
-
Check for iptables/nftables rules using OS fingerprint targetList iptables rules: `iptables -L -n -v` or `iptables -t mangle -L -n -v` and look for the --osf target. Also check nftables: `nft list ruleset` and search for osfAffected if There are firewall rules that use the OS fingerprinting target (--osf) which would invoke the vulnerable nf_osf_ttl function
-
Identify if traffic flows through the vulnerable code pathThe vulnerability triggers when nf_osf_ttl() processes packets with skb->dev potentially NULL, which occurs in container/virtualized environments or with certain network configurations. Monitor for kernel crashes or NULL pointer dereference errors in dmesg related to nf_osf or netfilterAffected if The system processes OS fingerprinting rules and experiences kernel NULL pointer dereference crashes in the netfilter subsystem, particularly in containerized or virtualized setups
A system is affected if it runs a vulnerable kernel version within the listed ranges AND has the netfilter OS fingerprinting module active with rules configured that trigger the nf_osf_ttl function path.
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 · scoped5.10.2585.15.2096.1.175
Apply the kernel security update containing the fix, which replaces the flawed device dereference and interface address loop with a switch statement that properly evaluates TTL according to ttl_check rules.
Upgrade to kernel version 6.6.141 or later (or the latest stable kernel in your current branch: 5.10.258+, 5.15.209+, or 6.1.175+)
- 1. Identify the current running kernel version using 'uname -r' or 'cat /proc/version'
- 2. Determine which kernel branch you're currently running (e.g., 5.10.x, 5.15.x, 6.1.x, 6.2+)
- 3. Upgrade the Linux kernel to a fixed version: for 5.10.x branch upgrade to >= 5.10.258, for 5.15.x upgrade to >= 5.15.209, for 6.1.x upgrade to >= 6.1.175, for 6.2+ upgrade to >= 6.6.141
- 4. For distribution kernels (Ubuntu, RHEL, Debian, etc.), apply the distribution's kernel update using standard package management (e.g., 'apt-get update && apt-get upgrade' for Debian/Ubuntu, 'yum update' for RHEL)
- 5. Reboot the system to load the new kernel
- 6. Verify the kernel version after reboot with 'uname -r' to confirm the fix is applied
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
- Implementation3.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-52998 — 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-2026-52998 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data