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CVE-2025-39770· NVD / CVE Program· CNA Linux

net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.37% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 041e2f945f82fdbd6fff577b79c33469430297aa, 2156d9e9f2e483c8c3906c0ea57ea312c1424235, 4.20; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.
  • Severity is disputed: the assigning authority (CNA) scores it 7.5, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 041e2f945f82fdbd6fff577b79c33469430297aa, 2156d9e9f2e483c8c3906c0ea57ea312c1424235, 4.20; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM When performing Generic Segmentation Offload (GSO) on an IPv6 packet that contains extension headers, the kernel incorrectly requests checksum offload if the egress device only advertises NETIF_F_IPV6_CSUM feature, which has a strict contract: it supports checksum offload only for plain TCP or UDP over IPv6 and explicitly does not support packets with extension headers. The current GSO logic violates this contract by failing to disable the feature for packets with extension headers, such as those used in GREoIPv6 tunnels. This violation results in the device being asked to perform an operation it cannot support, leading to a `skb_warn_bad_offload` warning and a collapse of network throughput. While device TSO/USO is correctly bypassed in favor of software GSO for these packets, the GSO stack must be explicitly told not to request checksum offload. Mask NETIF_F_IPV6_CSUM, NETIF_F_TSO6 and NETIF_F_GSO_UDP_L4 in gso_features_check if the IPv6 header contains extension headers to compute checksum in software. The exception is a BIG TCP extension, which, as stated in commit 68e068cabd2c6c53 ("net: reenable NETIF_F_IPV6_CSUM offload for BIG TCP packets"): "The feature is only enabled on devices that support BIG TCP TSO. The header is only present for PF_PACKET taps like tcpdump, and not transmitted by physical devices." kernel log output (truncated): WARNING: CPU: 1 PID: 5273 at net/core/dev.c:3535 skb_warn_bad_offload+0x81/0x140 ... Call Trace: <TASK> skb_checksum_help+0x12a/0x1f0 validate_xmit_skb+0x1a3/0x2d0 validate_xmit_skb_list+0x4f/0x80 sch_direct_xmit+0x1a2/0x380 __dev_xmit_skb+0x242/0x670 __dev_queue_xmit+0x3fc/0x7f0 ip6_finish_output2+0x25e/0x5d0 ip6_finish_output+0x1fc/0x3f0 ip6_tnl_xmit+0x608/0xc00 [ip6_tunnel] ip6gre_tunnel_xmit+0x1c0/0x390 [ip6_gre] dev_hard_start_xmit+0x63/0x1c0 __dev_queue_xmit+0x6d0/0x7f0 ip6_finish_output2+0x214/0x5d0 ip6_finish_output+0x1fc/0x3f0 ip6_xmit+0x2ca/0x6f0 ip6_finish_output+0x1fc/0x3f0 ip6_xmit+0x2ca/0x6f0 inet6_csk_xmit+0xeb/0x150 __tcp_transmit_skb+0x555/0xa80 tcp_write_xmit+0x32a/0xe90 tcp_sendmsg_locked+0x437/0x1110 tcp_sendmsg+0x2f/0x50 ... skb linear: 00000000: e4 3d 1a 7d ec 30 e4 3d 1a 7e 5d 90 86 dd 60 0e skb linear: 00000010: 00 0a 1b 34 3c 40 20 11 00 00 00 00 00 00 00 00 skb linear: 00000020: 00 00 00 00 00 12 20 11 00 00 00 00 00 00 00 00 skb linear: 00000030: 00 00 00 00 00 11 2f 00 04 01 04 01 01 00 00 00 skb linear: 00000040: 86 dd 60 0e 00 0a 1b 00 06 40 20 23 00 00 00 00 skb linear: 00000050: 00 00 00 00 00 00 00 00 00 12 20 23 00 00 00 00 skb linear: 00000060: 00 00 00 00 00 00 00 00 00 11 bf 96 14 51 13 f9 skb linear: 00000070: ae 27 a0 a8 2b e3 80 18 00 40 5b 6f 00 00 01 01 skb linear: 00000080: 08 0a 42 d4 50 d5 4b 70 f8 1a

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Sep 11, 2025
Updated
Oct 15, 2026
EPSS
0.3% · 29th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CNA vs NVD score

NVD
5.5
CNA · Linux
7.5
2.0 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • linux linux kernel5.4.285 and later · before 5.5
  • linux linux kernel5.10.229 and later · before 5.11
  • linux linux kernel5.15.171 and later · before 5.16
  • linux linux kernel6.1.116 and later · before 6.1.149
  • linux linux kernel6.6.60 and later · before 6.6.103
  • linux linux kernel4.19.323 and later · before 4.20
  • linux linux kernel6.12.1 and later · before 6.12.44
  • linux linux kernel6.13 and later · before 6.16.4
  • linux linux kernel6.11.7 and later · before 6.12
  • linux linux kernel6.12
  • linux linux kernel6.17

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • bcefc3cd7f592a70fcbbbfd7ad1fbc69172ea78b, 477b35d94a21530046fe91589960732fcf2b29ed, a27a5c40ee4cbe00294e2c76160de5f2589061ba, 9f605135a5c0fe614c2b15197b9ced1e217eca59, 705350fbd6ed4b5d89ee045fa57a0594a72b17d7, 6.12affected
    • a84978a9cda68f0afe3f01d476c68db21526baf1 and later · before a0478d7e888028f85fa7785ea838ce0ca09398e2affected · git
    • c69bc67c1cb211aa390bea6e512bb01b1241fefb and later · before 2156d9e9f2e483c8c3906c0ea57ea312c1424235affected · git
    • 04c20a9356f283da623903e81e7c6d5df7e4dc3c and later · before 041e2f945f82fdbd6fff577b79c33469430297aaaffected · git
    • 04c20a9356f283da623903e81e7c6d5df7e4dc3c and later · before 794ddbb7b63b6828c75967b9bcd43b086716e7a1affected · git
    • 04c20a9356f283da623903e81e7c6d5df7e4dc3c and later · before 864e3396976ef41de6cc7bc366276bf4e084fff2affected · git
    • 6.1.116 and later · before 6.1.149affected · semver
    • 6.6.60 and later · before 6.6.103affected · semver
    • 4.19.323 and later · before 4.20affected · semver
    • 5.4.285 and later · before 5.5affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.153-16.1.153-1
Debian:13linuxbefore 6.12.48-16.12.48-1
Debian:14linuxbefore 6.16.5-16.16.5-1
Red Hat:enterprise_linux:10.0kernelbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64kbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debugbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-debuginfobefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-develbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-devel-matchedbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-modulesbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-modules-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debug-modules-extrabefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-debuginfobefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-develbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-devel-matchedbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-modulesbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-modules-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-64k-modules-extrabefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-abi-stablelistsbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-debugbefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0
Red Hat:enterprise_linux:10.0kernel-debug-corebefore 0:6.12.0-55.33.1.el10_00:6.12.0-55.33.1.el10_0

+70

Same product

linux: all records

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux041e2f945f82fdbd6fff577b79c33469430297aaVendor (CNA)
Linux Linux2156d9e9f2e483c8c3906c0ea57ea312c1424235Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux5.11Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linux6.1.149Vendor (CNA)
Linux Linux6.12Vendor (CNA)
Linux Linux6.6.103Vendor (CNA)
Linux Linux794ddbb7b63b6828c75967b9bcd43b086716e7a1Vendor (CNA)
Linux Linux864e3396976ef41de6cc7bc366276bf4e084fff2Vendor (CNA)
Linux Linuxa0478d7e888028f85fa7785ea838ce0ca09398e2Vendor (CNA)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.1.153-1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-64k-debug-devel0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-64k-debug-devel-matched0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-64k-debuginfo0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-64k-devel0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-64k-devel-matched0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debug-debuginfo0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debug-devel0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debug-devel-matched0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debuginfo0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debuginfo-common-aarch640:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:kernel-debuginfo-common-ppc64le0:6.12.0-55.33.1.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records