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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-98377: vlan: require the MAC header to be present in __vlan_insert_inner_tag()

Noroxi assessment

Priority: Monitor (action score 0/100)

  • 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: 0.17% (FIRST EPSS).
  • Fixed version: Linux Linux 12295e0728488105b152b57fe8bc5e86f1d21a73, 3d531429524df2c7116579306640283fea68bcf0, 40a5cc4b7251c74f3341332a226d02200e96bccf; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1.

Low priority for now. Upgrade to Linux Linux 12295e0728488105b152b57fe8bc5e86f1d21a73, 3d531429524df2c7116579306640283fea68bcf0, 40a5cc4b7251c74f3341332a226d02200e96bccf; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1 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: vlan: require the MAC header to be present in __vlan_insert_inner_tag() __vlan_insert_inner_tag() only guarantees head room via skb_cow_head(), never that mac_len bytes of MAC header are present. Its ETH_HLEN wrappers - __vlan_insert_tag() under skb_vlan_push(), and vlan_insert_tag() under validate_xmit_vlan() on the generic transmit path - therefore rewrite the first 16 bytes at skb->data: a 12-byte memmove plus two 2-byte stores at +12 and +14. No caller supplies the bound, while the pop helpers use skb_ensure_writable()/pskb_may_pull(). An IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a one-byte AF_PACKET/SOCK_RAW frame. The first vlan push only sets a hwaccel tag; the next - clsact "action vlan push" or bpf_skb_vlan_push() - enters the helper with skb->len still 1. The head comes from skbuff_small_head without __GFP_ZERO, so each push drags bytes from beyond skb->tail into the frame. After three the one-byte send leaves as 13 bytes carrying 11 bytes of uninitialised slab: 0000: 5a b3 62 12 80 88 ff ff 00 b3 62 12 81 `------------------------------' only 0x5a was sent; the rest is slab, here the top 56 bits of a linear-map address Require the MAC header the helper rewrites to be present, so such a frame is dropped rather than transmitted.

—No exploit Fix available
Published
Oct 9, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 6th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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Noroxi analysis

What does it mean in your environment?

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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.

—

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

    • 2.6.12affected
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 12295e0728488105b152b57fe8bc5e86f1d21a73affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before aecace4ef31bd4e8ca1f224280ab52a457b0dc9aaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 50a958f865173e8752ff07bf0eff7b55cdeb5d74affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 3d531429524df2c7116579306640283fea68bcf0affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 40a5cc4b7251c74f3341332a226d02200e96bccfaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before f42562dd027dc4ed103fae17b2206e73ea1963c4affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdcaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before ab888242fce4f16f6c4d4c6ec53939ad36aa3b3aaffected · git
    • before 2.6.12not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:12linux-6.12before 6.12.113-1~deb12u16.12.113-1~deb12u1
Debian:13linuxbefore 6.12.113-16.12.113-1
Debian:14linuxbefore 7.2.9-17.2.9-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-98375Oct 9, 2026 · xen/netfront: drop RX packets with a short Ethernet header
    0Monitor
  • ← EarlierCVE-2026-98376Oct 9, 2026 · bpf: Use array_map_meta_equal for percpu array inner map replacement
    31Monitor
  • Later →CVE-2026-98378Oct 9, 2026 · bpf: Skip unsettled links in link iterator
    31Monitor

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 Linux12295e0728488105b152b57fe8bc5e86f1d21a73Vendor (CNA)
Linux Linux3d531429524df2c7116579306640283fea68bcf0Vendor (CNA)
Linux Linux40a5cc4b7251c74f3341332a226d02200e96bccfVendor (CNA)
Linux Linux50a958f865173e8752ff07bf0eff7b55cdeb5d74Vendor (CNA)
Linux Linux59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdcVendor (CNA)
Linux Linuxab888242fce4f16f6c4d4c6ec53939ad36aa3b3aVendor (CNA)
Linux Linuxaecace4ef31bd4e8ca1f224280ab52a457b0dc9aVendor (CNA)
Linux Linuxf42562dd027dc4ed103fae17b2206e73ea1963c4Vendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.159.1-1 on Azure Linux 3.06.6.161.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.12.113-1 · Debian:13Package registry (OSV)
debian:linux7.2.9-1 · Debian:14Package registry (OSV)
debian:linux-6.126.12.113-1~deb12u1 · Debian:12Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 7, 2026+30 d
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

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

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. Exploit maturity— → none
  2. Fix✗ → ✓

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

References

Show all references (7 more)

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

All records