Linux Kernel up to 6.18.13/6.19.3 ovpn ovpn_net_xmit use after free

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel up to 6.18.13/6.19.3. Affected by this issue is the function ovpn_net_xmit of the component ovpn. Executing a manipulation can lead to use after free. This vulnerability is handled as CVE-2026-45929. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.13/6.19.3. It has been declared as critical. This vulnerability affects the function ovpn_net_xmit of the component ovpn. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ovpn: fix possible use-after-free in ovpn_net_xmit When building the skb_list in ovpn_net_xmit, skb_share_check will free the original skb if it is shared. The current implementation continues to use the stale skb pointer for subsequent operations: - peer lookup, - skb_dst_drop (even though all segments produced by skb_gso_segment will have a dst attached), - ovpn_peer_stats_increment_tx. Fix this by moving the peer lookup and skb_dst_drop before segmentation so that the original skb is still valid when used. Return early if all segments fail skb_share_check and the list ends up empty. Also switch ovpn_peer_stats_increment_tx to use skb_list.next; the next patch fixes the stats logic.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-45929 since 05/13/2026. The exploitation appears to be easy. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 06/25/2026).

Upgrading to version 6.18.14 or 6.19.4 eliminates this vulnerability. Applying the patch 3e4fbcb4e078915367ba5576cd70d76dbc970f95/442915c96a9bff1c7080e2aedabb1c03faa28d81/a5ec7baa44ea3a1d6aa0ca31c0ad82edf9affe41 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.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.19.0
• 6.19.1
• 6.19.2
• 6.19.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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