Linux Kernel up to 6.6.139/6.12.85/6.18.26/7.0.3 skb_unshare use after free

CVSS Meta Temp Score
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CTI Interest Score
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7.7$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.6.139/6.12.85/6.18.26/7.0.3. This issue affects the function skb_unshare. Performing a manipulation results in use after free. This vulnerability is cataloged as CVE-2026-45998. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.6.139/6.12.85/6.18.26/7.0.3. This affects the function skb_unshare. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix potential UAF after skb_unshare() failure If skb_unshare() fails to unshare a packet due to allocation failure in rxrpc_input_packet(), the skb pointer in the parent (rxrpc_io_thread()) will be NULL'd out. This will likely cause the call to trace_rxrpc_rx_done() to oops. Fix this by moving the unsharing down to where rxrpc_input_call_event() calls rxrpc_input_call_packet(). There are a number of places prior to that where we ignore DATA packets for a variety of reasons (such as the call already being complete) for which an unshare is then avoided. And with that, rxrpc_input_packet() doesn't need to take a pointer to the pointer to the packet, so change that to just a pointer.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-45998 since 05/13/2026. The exploitability is told to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/19/2026).

The vulnerability scanner Nessus provides a plugin with the ID 321369 (Ubuntu 22.04 LTS : Linux kernel (Azure) vulnerabilities (USN-8440-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.140, 6.12.86, 6.18.27, 7.0.4 or 7.1-rc1 eliminates this vulnerability. Applying the patch e3bf143b1e98fb3d6d9e6825bcd683974d478e8c/bf20f46d94f1db38e6ffc0ca204a5fe0de01b495/996b0487b3cdda4c91811dbb1c9564626bc840bd/8fde6296c4d4da2be7ab761305ab7f232b94eefd/1f2740150f904bfa60e4bad74d65add3ccb5e7f8 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (321369). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

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Version

License

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.7

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CVSSv2info

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

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 321369
Nessus Name: Ubuntu 22.04 LTS : Linux kernel (Azure) vulnerabilities (USN-8440-1)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.140/6.12.86/6.18.27/7.0.4/7.1-rc1
Patch: e3bf143b1e98fb3d6d9e6825bcd683974d478e8c/bf20f46d94f1db38e6ffc0ca204a5fe0de01b495/996b0487b3cdda4c91811dbb1c9564626bc840bd/8fde6296c4d4da2be7ab761305ab7f232b94eefd/1f2740150f904bfa60e4bad74d65add3ccb5e7f8

Timelineinfo

05/13/2026 CVE reserved
05/27/2026 +14 days Advisory disclosed
05/27/2026 +0 days VulDB entry created
06/19/2026 +23 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-45998 (🔒)
GCVE (CVE): GCVE-0-2026-45998
GCVE (VulDB): GCVE-100-366249

Entryinfo

Created: 05/27/2026 17:21
Updated: 06/19/2026 13:55
Changes: 05/27/2026 17:21 (58), 06/16/2026 18:07 (11), 06/19/2026 13:55 (2)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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