CyberSecBulletin
CVE-2026-68299NVD status: Received

In the Linux kernel, the following vulnerability has been resolved: vmxnet3: fix BUG_ON in…

Published Updated By the CyberSecBulletin desk

CVE-2026-68299 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 2ddf51fcb6dd7d55ceef38e2e1a5ab2ab7fd47b0, fbab6b73cc086e32698c86e43d1b16bf17d24c36, 28e382646417c7e2be9c9a7079eddf627ff52b90 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 0.5% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 2ddf51fcb6dd7d55ceef38e2e1a5ab2ab7fd47b0 or fbab6b73cc086e32698c86e43d1b16bf17d24c36 or 28e382646417c7e2be9c9a7079eddf627ff52b90 or 667b6e52048eaf4dbcf1707ed87ffd44abb9cb38, whichever matches your release line, or a later version.
  2. 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
LinuxLinux45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 2ddf51fcb6dd7d55ceef38e2e1a5ab2ab7fd47b0; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, fbab6b73cc086e32698c86e43d1b16bf17d24c36; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 28e382646417c7e2be9c9a7079eddf627ff52b90; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 667b6e52048eaf4dbcf1707ed87ffd44abb9cb38; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 28cb5d8d13b4c1faf3f688f62e5df82fe7b438d8; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 4fdb0f162ccdbe9626863b10003855703253fa29; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, b28596baf87e25a078789f1c05817c8a3bf71257; 45dac1d6ea045ae56e4df8d9c70c92c7412bd4fc up to, but not including, 34a71f5361fc3adb5b7138da78750b0d535a8252; and 1 more ranges2ddf51fcb6dd7d55ceef38e2e1a5ab2ab7fd47b0, fbab6b73cc086e32698c86e43d1b16bf17d24c36, 28e382646417c7e2be9c9a7079eddf627ff52b90, 667b6e52048eaf4dbcf1707ed87ffd44abb9cb38, 28cb5d8d13b4c1faf3f688f62e5df82fe7b438d8, 4fdb0f162ccdbe9626863b10003855703253fa29

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: vmxnet3: fix BUG_ON in vmxnet3_get_hdr_len() for Geneve packets vmxnet3_get_hdr_len() assumes gdesc->rcd.v4/v6/tcp always describe the outer header, but for a Geneve-encapsulated packet the device can set them based on the inner header instead, signalled by the VMXNET3_RCD_HDR_INNER_SHIFT bit in the completion descriptor. Since the function never skips the outer encapsulation, this mismatch triggers: - BUG_ON(hdr.ipv4->protocol != IPPROTO_TCP), because the outer protocol is UDP (Geneve), not TCP. - BUG_ON(hdr.eth->h_proto != ...), when the tunnel's outer and inner IP versions differ (e.g. outer IPv6/inner IPv4 or vice versa). Check VMXNET3_RCD_HDR_INNER_SHIFT up front and bail out, since the function cannot locate the inner header it would need to parse. Also convert the remaining BUG_ON()s in this function to return 0 defensively.

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

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