Linux Kernel up to 7.2.8/7.3-rc4 IPv6 Networking dst_dev_overhead out-of-bounds write

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.8/7.3-rc4. Affected is the function dst_dev_overhead of the component IPv6 Networking. Executing a manipulation can lead to out-of-bounds write. This vulnerability is registered as CVE-2026-98570. It is possible to launch the attack remotely. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.8/7.3-rc4. It has been declared as very critical. This vulnerability affects the function dst_dev_overhead of the component IPv6 Networking. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. The CWE definition for the vulnerability is CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: keep room for the mac header in dst_dev_overhead() The seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as the length they are about to push plus dst_dev_overhead(), then push the new headers and rebuild the mac header below them with skb_mac_header_rebuild(). That rebuild needs skb->mac_len of headroom, but dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device, 16 bytes for plain Ethernet. Where the mac header is longer than that, as it is on ingress through a VLAN device with reorder_hdr off, the rebuild runs out of room: skb_set_mac_header(skb, -skb->mac_len) computes a negative offset, stores it unchecked in the u16 skb->mac_header, and the memmove that follows writes skb->mac_len bytes about 64 KB past skb->head. Forwarding plain ping6 traffic through such a device reproduces it on all five seg6 encapsulation modes and on the rpl and ioam6 inline paths; skb->mac_header comes back as 65534 on a 704-byte head. Return the larger of the two. The helper already returns skb->mac_len when it has no dst, so this only makes the other branch agree, and it covers every caller rather than each call site in turn.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-98570 since 09/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. 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 10/18/2026).

Upgrading to version 7.2.9 or 7.3-rc5 eliminates this vulnerability. Applying the patch 36c07127924f11fc5741a780abcaaf808fe9ef13/87cd6b717e4069dca34e0866e57eaeb44d3b173e is able to eliminate this problem. 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

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.2.8
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3
• 7.3-rc4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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