CyberSecBulletin
CVE-2026-53003NVD status: Modified

In the Linux kernel, the following vulnerability has been resolved: pppoe: drop PFC frames RFC…

Published Updated By the CyberSecBulletin desk

CVE-2026-53003 is a high-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions cb3beef35ab5e0c1afca9fd7648c6ae499786377, ba758fdf1399f310b30098b6faa3fd043de47dd2, fcca1df05322bb04e344dd1178b54b76a08eb7c3 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.72% chance of exploitation within 30 days, higher than 54% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to cb3beef35ab5e0c1afca9fd7648c6ae499786377 or ba758fdf1399f310b30098b6faa3fd043de47dd2 or fcca1df05322bb04e344dd1178b54b76a08eb7c3 or 8a5e840babc5c0fbd10c73728a13192347771ec6, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.258 or 5.15.209 or 6.1.175 or 6.6.141, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, cb3beef35ab5e0c1afca9fd7648c6ae499786377; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, ba758fdf1399f310b30098b6faa3fd043de47dd2; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, fcca1df05322bb04e344dd1178b54b76a08eb7c3; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, 8a5e840babc5c0fbd10c73728a13192347771ec6; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, 49e41b60ccd1bdbe9e218420f716dd5f9a2f9c71; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, 0cab5d077dd1efd2bd1a47271acc35894f945b4f; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, 2b5c3c040d020e3ab3b9a8887031202d96843b1e; 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 up to, but not including, cc1ff87bce1ccd38410ab10960f576dcd17db679; and 1 more rangescb3beef35ab5e0c1afca9fd7648c6ae499786377, ba758fdf1399f310b30098b6faa3fd043de47dd2, fcca1df05322bb04e344dd1178b54b76a08eb7c3, 8a5e840babc5c0fbd10c73728a13192347771ec6, 49e41b60ccd1bdbe9e218420f716dd5f9a2f9c71, 0cab5d077dd1efd2bd1a47271acc35894f945b4f
LinuxLinux Kernel5.0 up to, but not including, 5.10.258; 5.11 up to, but not including, 5.15.209; 5.16 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.105.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.

Official description

In 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

Spotted an error? Tell us.