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CVE-2026-98271 json

net: skbuff: do not leave stale header offsets after pskb_carve()

published last mo. modified 23d ago also EUVD-2026-93199

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: skbuff: do not leave stale header offsets after pskb_carve()

pskb_carve_inside_header() and pskb_carve_inside_nonlinear() remove the first bytes of a packet and reallocate skb->head.

All the headers that were present before the operation are gone, but both functions call skb_headers_offset_update(skb, 0), which is a no-op : skb->mac_header, skb->network_header, skb->transport_header and skb->csum_start keep their old values and now describe bytes which are no longer there.

Both helpers size the new head from the old skb_end_offset(), so the stale offsets still land inside the new allocation. They point past skb_tail_pointer() though, to bytes that were never initialized.

pskb_carve_inside_nonlinear() is the worst case, because it leaves a zombie skb with an empty linear part (skb->data == skb_tail_pointer(skb), skb_headlen(skb) == 0), while skb_mac_header_was_set() is still true and skb->mac_header is way ahead of skb->data.

The only user of pskb_extract() is rds_tcp_data_recv(), and the carved skb is queued on tinc->ti_skb_list. When the RDS incoming message is released, rds_tcp_inc_free() calls skb_queue_purge(), which frees the skbs with SKB_DROP_REASON_QUEUE_PURGE. This is visible from drop_monitor, which then tries to pull back to the (bogus) mac header :

skbuff: __skb_pull(len=234) skb len=6968 data_len=6968 headroom=0 headlen=0 tailroom=0 end-tail=384 mac=(234,14) mac_len=14 net=(248,40) trans=288 shinfo(txflags=0 nr_frags=1 gso(size=1428 type=16 segs=5)) csum(0x100120 start=288 offset=16 ip_summed=3 complete_sw=0 valid=1 level=0) hash(0x7b446c6c sw=0 l4=1) proto=0x86dd pkttype=0 iif=60 kernel BUG at ./include/linux/skbuff.h:2847!

Add skb_carve_reset_headers() to mark the mac and transport headers as not set, reset the network header, clear skb->mac_len, and drop a now meaningless CHECKSUM_PARTIAL (csum_start no longer describes anything).

Invalidate the inner offsets as well. Unlike mac_header and transport_header they have no "unset" sentinel, so a leftover non-zero value still looks like a real header. Zero skb->inner_mac_header, skb->inner_network_header, skb->inner_transport_header, skb->inner_protocol and skb->encapsulation, so that all the header state is invalidated in one place.

v2: fixed an inaccurate changelog. The stale offsets stay inside the new skb->head, which is never smaller than the old one, they simply point past skb_tail_pointer() to bytes that are gone. Thanks to Xuanqiang Luo for insisting on this. Also invalidate the inner header state, as suggested by the netdev AI review : https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260911114922.621937-1-edumazet%40google.com

Patch / fix

  • Linux Linux 7.3
  • linux Debian 13 6.12.113-1
  • linux Debian 14 7.2.8-1
  • linux-6.12 Debian 12 6.12.113-1~deb12u1

debian advisories DEBIAN-CVE-2026-98271

  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-42.42.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1015.16
  • linux-hwe-7.0 Ubuntu 24.04 LTS 7.0.0-42.42~24.04.1
  • linux-oem-7.0 Ubuntu 26.04 LTS 7.0.0-1017.17

ubuntu advisories UBUNTU-CVE-2026-98271

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source openSUSE Tumbleweed 7.2.10-1.1

opensuse advisories openSUSE-SU-2026:12131-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-98271 updated cvss 5.9

kernel: net: skbuff: do not leave stale header offsets after pskb_carve()

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-11).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.