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Fencer Vulns
high 8.6

CVE-2026-80590 json

inet: frags: strip GSO state from fragments before reassembly

published 2026-08-28 2 mo ago modified 2026-10-19 21 d ago also EUVD-2026-67580

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

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

inet: frags: strip GSO state from fragments before reassembly

A virtio_net_hdr (tun/tap, or AF_PACKET with PACKET_VNET_HDR) can mark an IPv4 or IPv6 fragment as GSO; nothing relates gso_type to frag_off. inet_frag_reasm_prepare()/inet_frag_reasm_finish() keep the first fragment's skb as the head of the reassembled datagram, including its shinfo->gso_size/gso_type/gso_segs, and chain the remaining fragments on frag_list with whatever linear/paged layout they arrived with.

After ip_defrag() (ip_local_deliver(), nf_defrag_ipv4, ...) the reassembled skb therefore still claims to be GSO (SKB_GSO_DODGY), and the next software segmentation point - udp_rcv_segment() on local delivery, validate_xmit_skb(), or the ip_finish_output_gso() slow path - hands it to skb_segment(). skb_segment()'s frag_list walk assumes GRO-shaped input and hits one of its BUG_ON()s. Two writes to a tap by an unprivileged user in its own userns are enough:

kernel BUG at net/core/skbuff.c:4899! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 1000 PID: 82 Comm: poc Not tainted 7.2.0-pentest+ #2 RIP: 0010:skb_segment+0x20ca/0x48b0 Call Trace: <TASK> __udp_gso_segment+0x29a/0x27d0 udp4_ufo_fragment+0x458/0x6c0 inet_gso_segment+0x429/0x1340 skb_mac_gso_segment+0x233/0x4f0 __skb_gso_segment+0x308/0x660 udp_queue_rcv_skb+0x440/0xad0 udp_unicast_rcv_skb+0xc7/0x2c0 udp_rcv+0x16ce/0x2260 ip_protocol_deliver_rcu+0x197/0x2d0 ip_local_deliver+0x430/0x690 ip_rcv+0x16f/0x1f0 __netif_receive_skb_one_core+0x15e/0x1c0 __netif_receive_skb+0x1e/0x110 netif_receive_skb+0xf6/0x5c0 tun_rx_batched.isra.0+0x3ab/0x790 tun_get_user+0x17c3/0x3550 tun_chr_write_iter+0xba/0x1b0 vfs_write+0x646/0x1130 </TASK> Kernel panic - not syncing: Fatal exception in interrupt

This runs with BH disabled, so it is a panic rather than an oops. The same is reachable with CAP_NET_RAW in a netns where a defrag point precedes a GSO point, and from a guest whose VMM forwards virtio_net_hdr to a tap. The SKB_GSO_DODGY frag_list checks added by commit 3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag_list") and by commit 9e4b7a99a03a ("net: gso: fix panic on frag_list with mixed head alloc types") do not cover it: page-backed heads skip them, and kmalloc heads skip them when gso_size == skb_headlen(head), which the sender controls.

An skb entering a frag queue is an IP fragment by definition and cannot legitimately carry GSO state: GRO does not merge fragments and the stack segments before it fragments, so only untrusted sources are affected. This has been reachable since commit f43798c27684 ("tun: Allow GSO using virtio_net_hdr"), the first path that let userspace attach GSO metadata to an IP fragment. Reset the GSO fields of every fragment as it is queued, in inet_frag_queue_insert(), which IPv4, IPv6, nf_conntrack_reasm and 6lowpan reassembly share; then neither the head nor the frag_list members of the reassembled skb carry them (the members matter too: the ip_do_fragment()/ip6_fragment() fast paths send them out as they are). The head may remain CHECKSUM_PARTIAL; that is already accepted on receive and resolved by skb_checksum_help() in ip_do_fragment()/ip6_fragment() on forward.

Tested on top of net.git (dc4b95b8fee9), x86_64: the tap reproducer above, two further IPv4 frag_list geometries that reach BUG_ON(i >= nfrags) and BUG_ON(!list_skb->head_frag), and an IPv6 fragment-header variant (udp6_ufo_fragment()) each panic the unpatched kernel; with this patch all four datagrams are delivered intact and nothing is logged.

Patch / fix

  • Linux Linux 5.10.268, 5.15.219, 6.1.186, 6.6.155, 6.12.107, 6.18.48, 7.1.12, 7.2.2, 7.3
  • linux Debian 12 6.1.187-1
  • linux Debian 13 6.12.107-1
  • linux Debian 14 7.1.12-1
  • linux-6.12 Debian 12 6.12.107-1~deb12u1

debian advisories DEBIAN-CVE-2026-80590

  • linux Ubuntu 22.04 LTS 5.15.0-202.212
  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1115.121
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1113.117

ubuntu advisories UBUNTU-CVE-2026-80590

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-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:4282-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1openSUSE-SU-2026:11648-1

  • kernel AlmaLinux 10 6.12.0-211.68.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.68.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.68.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.68.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.68.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.68.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.68.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.68.1.el10_2

almalinux advisories ALSA-2026:88477ALSA-2026:87374ALSA-2026:87375ALSA-2026:86033

  • kernel Rocky Linux 10 6.12.0-211.68.1.el10_2
  • kernel-rt Rocky Linux 8 4.18.0-553.177.1.rt7.518.el8_10
  • kernel Rocky Linux 8 4.18.0-553.177.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.59.1.el9_8

rocky linux advisories RLSA-2026:88477RLSA-2026:87374RLSA-2026:87375RLSA-2026:86033

  • kernel Azure Linux 3.0 6.6.157.1-1

azure linux advisories AZL-98117

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-80590 updated cvss 7.7

kernel: inet: frags: strip GSO state from fragments before reassembly

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: workaround, no fix available
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.68.1.el10_2
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.59.1.el9_8, perf 5.14.0-687.59.1.el9_8, rtla 5.14.0-687.59.1.el9_8, python3-perf 5.14.0-687.59.1.el9_8, kernel-devel-matched 5.14.0-687.59.1.el9_8, kernel-64k-devel-matched 5.14.0-687.59.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.68.1.el10_2, perf 6.12.0-211.68.1.el10_2, rtla 6.12.0-211.68.1.el10_2, python3-perf 6.12.0-211.68.1.el10_2, kernel-devel-matched 6.12.0-211.68.1.el10_2, kernel-64k-devel-matched 6.12.0-211.68.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.177.1.el8_10, kernel 4.18.0-553.177.1.el8_10, bpftool 4.18.0-553.177.1.el8_10, kernel-core 4.18.0-553.177.1.el8_10, kernel-tools 4.18.0-553.177.1.el8_10, python3-perf 4.18.0-553.177.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:87375
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.59.1.el9_8, kernel-64k 5.14.0-687.59.1.el9_8, kernel-core 5.14.0-687.59.1.el9_8, kernel-tools 5.14.0-687.59.1.el9_8, kernel-modules 5.14.0-687.59.1.el9_8, kernel-64k-core 5.14.0-687.59.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.68.1.el10_2, kernel-64k 6.12.0-211.68.1.el10_2, kernel-core 6.12.0-211.68.1.el10_2, kernel-tools 6.12.0-211.68.1.el10_2, kernel-modules 6.12.0-211.68.1.el10_2, kernel-64k-core 6.12.0-211.68.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.59.1.el9_8
    fixed: vendor fix RHSA-2026:86033
show 10 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.68.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.68.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.68.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.68.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.68.1.el10_2
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.177.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.177.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.177.1.el8_10
    fixed: vendor fix RHSA-2026:87375
  • Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.68.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.68.1.el10_2
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-kvm 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-core 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-modules 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-debug-kvm 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-debug-core 4.18.0-553.177.1.rt7.518.el8_10, +4 more
    fixed: vendor fix RHSA-2026:87374
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.59.1.el9_8, kernel-rt-64k 5.14.0-687.59.1.el9_8, kernel-rt-core 5.14.0-687.59.1.el9_8, kernel-rt-modules 5.14.0-687.59.1.el9_8, kernel-rt-64k-core 5.14.0-687.59.1.el9_8, kernel-rt-debug-core 5.14.0-687.59.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.68.1.el10_2, kernel-rt-64k 6.12.0-211.68.1.el10_2, kernel-rt-core 6.12.0-211.68.1.el10_2, kernel-rt-modules 6.12.0-211.68.1.el10_2, kernel-rt-64k-core 6.12.0-211.68.1.el10_2, kernel-rt-debug-core 6.12.0-211.68.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.59.1.el9_8, kernel-rt-core 5.14.0-687.59.1.el9_8, kernel-rt-modules 5.14.0-687.59.1.el9_8, kernel-rt-debug-core 5.14.0-687.59.1.el9_8, kernel-rt-modules-core 5.14.0-687.59.1.el9_8, kernel-rt-debug-modules 5.14.0-687.59.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.68.1.el10_2, kernel-rt-core 6.12.0-211.68.1.el10_2, kernel-rt-modules 6.12.0-211.68.1.el10_2, kernel-rt-debug-core 6.12.0-211.68.1.el10_2, kernel-rt-modules-core 6.12.0-211.68.1.el10_2, kernel-rt-debug-modules 6.12.0-211.68.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:88477
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-core 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-modules 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-debug-core 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-debug-modules 4.18.0-553.177.1.rt7.518.el8_10, kernel-rt-modules-extra 4.18.0-553.177.1.rt7.518.el8_10, +2 more
    fixed: vendor fix RHSA-2026:87374
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
23 d ago

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns 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.