Linux azure: In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv() Blamed commit did not… (CVE-2026-23003)
A vulnerability in the Linux kernel's IPv6 tunnel handling was resolved by using skb_vlan_inet_prepare() in the __ip6_tnl_rcv() function to properly handle VLAN encapsulations. The issue was identified by syzbot and involved uninitialized values in ECN decapsulation code. This flaw could lead to a denial of service (system crash) due to kernel memory corruption. The vulnerability affects multiple Linux Azure kernel versions prior to specific patched releases. A fix is available and included in updated kernel packages.
AI Analysis
Technical Summary
The vulnerability in the Linux kernel (CVE-2026-23003) concerns the ip6_tunnel subsystem where the function __ip6_tnl_rcv() did not correctly handle VLAN encapsulations, failing to use skb_vlan_inet_prepare() and instead using pskb_inet_may_pull(). This caused uninitialized value usage in ECN decapsulation routines, potentially leading to kernel memory corruption and denial of service. The issue was detected by syzbot and has been fixed by correcting the code to use skb_vlan_inet_prepare(). The fix is included in updated Linux Azure kernel packages.
Potential Impact
An attacker could exploit this vulnerability to cause a denial of service by crashing the kernel due to memory corruption. There is no indication of confidentiality or integrity impact. The CVSS score is 7.5 (medium severity) with network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.
Mitigation Recommendations
A patch is available and should be applied by updating to the fixed Linux Azure kernel versions as provided by the vendor. The vendor advisory from Ubuntu confirms that the issue is resolved in updated packages. After updating, a system reboot is required. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be necessary. Users should follow the vendor's update instructions to remediate this vulnerability.
Linux azure: In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv() Blamed commit did not… (CVE-2026-23003)
Description
A vulnerability in the Linux kernel's IPv6 tunnel handling was resolved by using skb_vlan_inet_prepare() in the __ip6_tnl_rcv() function to properly handle VLAN encapsulations. The issue was identified by syzbot and involved uninitialized values in ECN decapsulation code. This flaw could lead to a denial of service (system crash) due to kernel memory corruption. The vulnerability affects multiple Linux Azure kernel versions prior to specific patched releases. A fix is available and included in updated kernel packages.
CVSS v3.1
Score 7.5high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in the Linux kernel (CVE-2026-23003) concerns the ip6_tunnel subsystem where the function __ip6_tnl_rcv() did not correctly handle VLAN encapsulations, failing to use skb_vlan_inet_prepare() and instead using pskb_inet_may_pull(). This caused uninitialized value usage in ECN decapsulation routines, potentially leading to kernel memory corruption and denial of service. The issue was detected by syzbot and has been fixed by correcting the code to use skb_vlan_inet_prepare(). The fix is included in updated Linux Azure kernel packages.
Potential Impact
An attacker could exploit this vulnerability to cause a denial of service by crashing the kernel due to memory corruption. There is no indication of confidentiality or integrity impact. The CVSS score is 7.5 (medium severity) with network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.
Mitigation Recommendations
A patch is available and should be applied by updating to the fixed Linux Azure kernel versions as provided by the vendor. The vendor advisory from Ubuntu confirms that the issue is resolved in updated packages. After updating, a system reboot is required. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be necessary. Users should follow the vendor's update instructions to remediate this vulnerability.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-23003
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:FIPS-updates:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:FIPS-updates:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Nvidia-BlueField:22.04:LTS","Ubuntu:Pro:FIPS-updates:22.04:LTS","Ubuntu:Pro:Realtime:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Nvidia-BlueField:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:Pro:Realtime:24.04:LTS","Ubuntu:25.10"]
- Cvss Version
- 3.1
Threat ID: 6a5b636f2d1edb114c8b46e3
Added to database: 07/18/2026, 11:28:47 UTC
Last enriched: 08/22/2026, 21:46:43 UTC
Last updated: 09/10/2026, 19:36:52 UTC
Views: 7
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