Linux KernelOperating system · Linux
CVE-2026-53003
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: pppoe: drop PFC frames RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT RECOMMENDED for PPPoE. In practice, pppd does not support negotiating PFC for PPPoE sessions, and the current PPPoE driver assumes an uncompressed (2-byte) protocol field. However, the generic PPP layer function ppp_input() is not aware of the negotiation result, and still accepts PFC frames. If a peer with a broken implementation or an attacker sends a frame with a compressed (1-byte) protocol field, the subsequent PPP payload is shifted by one byte. This causes the network header to be 4-byte misaligned, which may trigger unaligned access exceptions on some architectures. To reduce the attack surface, drop PPPoE PFC frames. Introduce ppp_skb_is_compressed_proto() helper function to be used in both ppp_generic.c and pppoe.c to avoid open-coding.
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 Linux kernel's PPPoE driver assumes a 2-byte (uncompressed) protocol field in PPPoE frames, but the generic PPP layer accepts 1-byte compressed Protocol Field Compression (PFC) frames. When a PFC frame is received from a peer or attacker, the PPP payload shifts by one byte, causing 4-byte misalignment of network headers that triggers unaligned access exceptions on some architectures.
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
>= 5.0, < 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.
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Check the running kernel versionRun `uname -r` or `cat /proc/version` to obtain the kernel version, then compare it against the affected ranges: >= 5.0 and < 5.10.258; >= 5.11 and < 5.15.209; >= 5.16 and < 6.1.175; >= 6.2 and < 6.6.141; >= 6.7 and < 6.12.91; >= 6.13 and < 6.18.33; >= 6.19 and < 7.0.10Affected if The kernel version falls within any of the listed vulnerable ranges
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Verify if PPPoE is in use on the systemCheck for active PPP interfaces by running `ip link show | grep -i ppp` or `ls /sys/class/net/ | grep -E '^ppp'`, and examine `/etc/ppp/` for configuration filesAffected if The system has active PPP or PPPoE interfaces configured
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Check for loaded PPP-related kernel modulesRun `lsmod | grep -E '(ppp|pppoe)'` to see if ppp_generic, pppoe, or related modules are loadedAffected if PPP or PPPoE kernel modules are loaded in memory
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Inspect network traffic for PPPoE framesUse packet capture tools such as `tcpdump -i <interface> -v | grep -i proto` or check network logs for incoming PPPoE traffic, particularly looking for 1-byte protocol field indicatorsAffected if The system is receiving PPPoE traffic, especially if the peer sends compressed protocol fields (0x00 or 0x0f prefix)
The system is affected if it runs a vulnerable kernel version AND has PPPoE interfaces active or configured, as the flaw triggers when compressed PPP protocol field frames are received on a PPPoE connection.
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
Drop PPPoE PFC frames at the PPPoE driver level as per RFC 2516 recommendation, and use the new ppp_skb_is_compressed_proto() helper to validate protocol fields consistently.
Linux Kernel 5.10.258, 5.15.209, 6.1.175, or 6.6.141 (depending on which major version branch you are on)
- 1. Identify the current running kernel version using `uname -r`
- 2. Check if the current version falls within any of the affected ranges: >= 5.0 and < 5.10.258, >= 5.11 and < 5.15.209, >= 5.16 and < 6.1.175, or >= 6.2 and < 6.6.141
- 3. If affected, plan for a kernel upgrade to a fixed version: upgrade to 5.10.258 or later if on 5.x, 5.15.209 or later if on 5.11-5.15, 6.1.175 or later if on 5.16-6.1, or 6.6.141 or later if on 6.2+
- 4. Obtain the kernel update from your distribution's official repositories (e.g., `apt update && apt upgrade` for Debian/Ubuntu, `yum update` for RHEL/CentOS, or `dnf update` for Fedora)
- 5. After upgrading, reboot the system to load the fixed kernel
- 6. Verify the fix is applied by checking the kernel version and that the pppoe module loads correctly
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
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 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-2026-53003 — 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-2026-53003 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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