VulnerabilityPublished 27 Dec 2024Updated 3 Nov 2025

CVE-2024-56636: Linux kernel · geneve: do not assume mac header is set in geneve_xmit_skb()

Source GCVE Database

Compare

Not known to be exploited · CVSS 5.5 Medium.

Data as of 30 Oct 2026, 00:51 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-w8fg-7596-644q

What to do

AI-suggested

A fix is available that replaces the unsafe eth_hdr() call with skb_eth_hdr() in the geneve_xmit_skb() function. Users should update their Linux kernel to a version that includes this fix. Since this is a kernel-level issue, applying the official kernel patch or upgrading to a fixed kernel release is the recommended remediation.

Description

CVE-2024-56636 is a medium severity vulnerability in the Linux kernel's Geneve network driver. The issue arises because the code incorrectly assumes that the MAC header is always set in the geneve_xmit_skb() function. This assumption can lead to warnings or potential instability during packet transmission. The flaw is addressed by using skb_eth_hdr() instead of eth_hdr() to safely access the MAC header.

Impact

The vulnerability does not impact confidentiality or integrity but can cause kernel warnings and potentially lead to denial of service by crashing or destabilizing the network driver during packet transmission. The CVSS score of 5.5 reflects a medium severity with local attack vector, low complexity, and no user interaction required. There is no indication of exploitation in the wild.

Summary

This vulnerability in the Linux kernel's Geneve driver involves an incorrect assumption that the MAC header is set in the output path within the geneve_xmit_skb() function. The code previously used eth_hdr(), which assumes the MAC header is set, but this is not always the case. The fix replaces eth_hdr() with skb_eth_hdr(), which correctly handles cases where the MAC header may not be set, preventing kernel warnings and potential crashes. The issue was identified through kernel warnings triggered by sysbot and affects the packet transmission path in the Geneve driver.

References

Community reviews

Loading reviews…