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CVE-2026-98570

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Last modified

CVE-2026-98570 is a vulnerability of currently unknown severity. 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.

Description

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.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= dce525185bc92864e5a318040285ee070563fe34, < 36c07127924f11fc5741a780abcaaf808fe9ef13; >= dce525185bc92864e5a318040285ee070563fe34, < 87cd6b717e4069dca34e0866e57eaeb44d3b173e; 8471e228448a818e4c27cab4b681b2e758e46cf5; c432cd18a07b623651ed15ea167bd303467004cc; 634710a372ba65bee667c2f6e58a97658c639eab; c447c5a9c47bb4858ab12bf90879fe595d2b7f46; ab9de9c48316d2622d3bf353916b99971570e2c9; 2fcc9f3798ef82399564d247458e69abd10e683b; 371d8dc298b4f59e99b4564ac5d906fce0932c69; b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3; c0b11dc50590e10590b39dcda79835cd32f49d00; 4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5; 25d8e065c7972dc98fd7a4cac322d5367eaede88; 4a855c5aec41bf84922224ab7a74e088776e3ac4; a9f0407414e16176fdbbbd298c9e18d6dfdf96bc; >= 6.12.16, < 6.13; >= 6.13.4, < 6.14; >= 5.15.179, < 5.16; >= 6.1.130, < 6.2; >= 6.6.81, < 6.7; >= 5.10.235, < 5.11
LinuxLinux6.14

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-98570?
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.
How severe is CVE-2026-98570?
Severity scoring for CVE-2026-98570 is pending analysis.
How do I fix CVE-2026-98570?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST