VulnerabilityPublished 15 Aug 2026Updated 9 Oct 2026

CVE-2026-72348: Linux kernel · netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop

Affects Linux kernelSource GCVE Database

Not known to be exploited · CVSS 9.1 Critical · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +43

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

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

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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-mf85-825j-jwwx

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected <7.0.0-34.34	Fixed in 7.0.0-34.34
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected <7.0.0-1013.13	Fixed in 7.0.0-1013.13
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected <7.0.0-1017.17	Fixed in 7.0.0-1017.17
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected <7.0.0-1016.16	Fixed in 7.0.0-1016.16
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected <7.0.0-1013.13	Fixed in 7.0.0-1013.13
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected <7.0.0-1007.8	Fixed in 7.0.0-1007.8

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

An official patch is available and should be applied to affected Linux kernel versions to correct the advertised-length validation and ensure malformed IPv6 packets are dropped. The vendor advisory confirms the issue is fixed. Users should update to patched kernel versions to mitigate this vulnerability.

Description

A vulnerability in the Linux kernel's netfilter ip6tables subsystem was resolved that involved improper handling of malformed IPv6 extension headers. Specifically, the vulnerability related to the ah, hbh, and rt matches not properly validating the advertised extension header length, which could allow malformed packets to bypass intended filtering rules. The issue was fixed by adding and updating advertised-length checks and ensuring malformed packets are dropped. This vulnerability affects specific Linux kernel versions and has a high CVSS score of 9.1, indicating critical impact on confidentiality and integrity without availability impact. A patch is available to address this issue.

Impact

The vulnerability allows malformed IPv6 extension header packets to bypass ip6tables filtering rules, potentially enabling attackers to circumvent network security policies. The CVSS score of 9.1 reflects a critical impact on confidentiality and integrity, meaning attackers could exploit this to compromise system security. There is no indication of availability impact. No known exploits in the wild have been reported at this time.

Summary

The Linux kernel netfilter ip6tables subsystem had a vulnerability where the ah, hbh, and rt IPv6 extension header matches did not correctly validate the advertised extension header length. This allowed malformed IPv6 extension headers to bypass filtering rules because the hotdrop flag was not set properly before returning false on length validation failures. The fix involved adding missing advertised-length checks for the ah match, updating checks for hbh and rt matches, and setting hotdrop to true to drop malformed packets, preventing them from bypassing ip6tables rules. This vulnerability affects multiple specific Linux kernel versions and has been assigned CVE-2026-72348 with a CVSS 3.1 score of 9.1.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 08:25 UTC

Technical details

References

Community reviews

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