Linux Kernel up to 6.12.108/6.18.49/7.2.3 Tun tun_get_user align allocation of resources

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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9.5$0-$5k0.00+

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 6.12.108/6.18.49/7.2.3. This impacts the function tun_get_user of the component Tun. The manipulation of the argument align results in allocation of resources. This vulnerability is cataloged as CVE-2026-81000. The attack may be launched remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.108/6.18.49/7.2.3. It has been classified as very critical. Affected is the function tun_get_user of the component Tun. The manipulation of the argument align with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2026-81000 since 08/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/12/2026). This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 6.12.109, 6.18.50, 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 379d85c7f25f3e05a428225e6b8a65613c6e9b9d/e098d9cc8859614a7f7baebc96e32a5a16b18ed2/0ada54ea63e48b9c1608e917ccb7dfadbe86db28/447c9303942c439a117d9b76ce6d6e2116b38ee7 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.9
VulDB Meta Temp Score: 9.5

VulDB Base Score: 9.9
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Allocation of resources
CWE: CWE-770 / CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.12.109/6.18.50/7.2.4/7.3-rc1
Patch: 379d85c7f25f3e05a428225e6b8a65613c6e9b9d/e098d9cc8859614a7f7baebc96e32a5a16b18ed2/0ada54ea63e48b9c1608e917ccb7dfadbe86db28/447c9303942c439a117d9b76ce6d6e2116b38ee7

Timelineinfo

08/26/2026 CVE reserved
09/11/2026 +16 days VulDB entry created
09/12/2026 +0 days Advisory disclosed
09/12/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-81000 (🔒)
GCVE (CVE): GCVE-0-2026-81000
GCVE (VulDB): GCVE-100-402774

Entryinfo

Created: 09/12/2026 00:28
Changes: 09/12/2026 00:28 (60)
Complete: 🔍
Cache ID: 216::103

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