CVE-2026-98377
vlan: require the MAC header to be present in __vlan_insert_inner_tag()
No known exploitation. EPSS puts it in the 4th percentile. Fixed versions are out.
What to do
Find your product and version, then upgrade to the build on the right.
- LinuxAffected: ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 40a5cc4b7251c74f3341332a226d02200e96bccfUpgrade to: 40a5cc4b7251c74f3341332a226d02200e96bccfAffected: ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < f42562dd027dc4ed103fae17b2206e73ea1963c4Upgrade to: f42562dd027dc4ed103fae17b2206e73ea1963c4Affected: ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdcUpgrade to: 59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdcAffected: ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ab888242fce4f16f6c4d4c6ec53939ad36aa3b3aUpgrade to: ab888242fce4f16f6c4d4c6ec53939ad36aa3b3aStated by: CVE record
Versions as the sources state them. Full version matrix after sign-in
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.2% chance of exploitation activity in the next 30 days, which ranks it in the 4th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
2 events over 0 days, from the signal feeds we watch.
- Publishedrecord updated
Affected products
Sources
References in the record
- git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf
- git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4
- git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc
And 1 more reference. See all after sign-in
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