In the Linux kernel, the following vulnerability has been resolved:
xfrm: iptfs: fix runt reassembly panic from short inner tot_len
When the start of an inner packet is split across two outer packets
such that fewer than 4 bytes land at the end of the first one,
__input_process_payload() saves those bytes as a runt and skips the
iplen/iphlen validation performed for in-place packets. When the
continuation packet arrives, iptfs_reassem_cont() only requires the
declared inner length to be >= sizeof(ra_runt) (6) before allocating
the reassembly skb with that attacker-controlled length.
However, __iptfs_iphlen() always returns the fixed minimum IP header
size (20 for IPv4, 40 for IPv6), so for an inner IPv4 tot_len in
[6, 19] the header-completion copy writes past the declared packet
length, and the subsequent "ipremain -= copylen" underflows to ~4GB,
leaving the payload copy length bounded only by blkoff (up to 64KB).
At runtime the skb_put() tailroom check turns this into
skb_over_panic(), i.e. an unprivileged kernel panic (DoS), reachable
locally via userns+netns IPTFS SAs and remotely against IPTFS VPN
gateways when the decrypted outer skb is linear (e.g. AF_PACKET taps,
tun/tap delivery).
Align the runt path with the normal path by requiring the declared
inner length to cover at least the IP header size. This also subsumes
the previous >= sizeof(ra_runt) check, since the minimum IP header
is always larger than the runt buffer.
This issue was found by the autokbug dynamic kernel fuzzer at
Tencent Yunding Lab.
xfrm: iptfs: fix runt reassembly panic from short inner tot_len
When the start of an inner packet is split across two outer packets
such that fewer than 4 bytes land at the end of the first one,
__input_process_payload() saves those bytes as a runt and skips the
iplen/iphlen validation performed for in-place packets. When the
continuation packet arrives, iptfs_reassem_cont() only requires the
declared inner length to be >= sizeof(ra_runt) (6) before allocating
the reassembly skb with that attacker-controlled length.
However, __iptfs_iphlen() always returns the fixed minimum IP header
size (20 for IPv4, 40 for IPv6), so for an inner IPv4 tot_len in
[6, 19] the header-completion copy writes past the declared packet
length, and the subsequent "ipremain -= copylen" underflows to ~4GB,
leaving the payload copy length bounded only by blkoff (up to 64KB).
At runtime the skb_put() tailroom check turns this into
skb_over_panic(), i.e. an unprivileged kernel panic (DoS), reachable
locally via userns+netns IPTFS SAs and remotely against IPTFS VPN
gateways when the decrypted outer skb is linear (e.g. AF_PACKET taps,
tun/tap delivery).
Align the runt path with the normal path by requiring the declared
inner length to cover at least the IP header size. This also subsumes
the previous >= sizeof(ra_runt) check, since the minimum IP header
is always larger than the runt buffer.
This issue was found by the autokbug dynamic kernel fuzzer at
Tencent Yunding Lab.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
No data.
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 06 Oct 2026 09:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: xfrm: iptfs: fix runt reassembly panic from short inner tot_len When the start of an inner packet is split across two outer packets such that fewer than 4 bytes land at the end of the first one, __input_process_payload() saves those bytes as a runt and skips the iplen/iphlen validation performed for in-place packets. When the continuation packet arrives, iptfs_reassem_cont() only requires the declared inner length to be >= sizeof(ra_runt) (6) before allocating the reassembly skb with that attacker-controlled length. However, __iptfs_iphlen() always returns the fixed minimum IP header size (20 for IPv4, 40 for IPv6), so for an inner IPv4 tot_len in [6, 19] the header-completion copy writes past the declared packet length, and the subsequent "ipremain -= copylen" underflows to ~4GB, leaving the payload copy length bounded only by blkoff (up to 64KB). At runtime the skb_put() tailroom check turns this into skb_over_panic(), i.e. an unprivileged kernel panic (DoS), reachable locally via userns+netns IPTFS SAs and remotely against IPTFS VPN gateways when the decrypted outer skb is linear (e.g. AF_PACKET taps, tun/tap delivery). Align the runt path with the normal path by requiring the declared inner length to cover at least the IP header size. This also subsumes the previous >= sizeof(ra_runt) check, since the minimum IP header is always larger than the runt buffer. This issue was found by the autokbug dynamic kernel fuzzer at Tencent Yunding Lab. | |
| Title | xfrm: iptfs: fix runt reassembly panic from short inner tot_len | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-06T08:46:55.753Z
Reserved: 2026-09-25T10:25:14.344Z
Link: CVE-2026-98371
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-06T09:18:31.613
Modified: 2026-10-06T09:18:31.613
Link: CVE-2026-98371
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.