CVE-2026-81000net: tun: bound receive headroom
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from eaea34b23c46bf17b4a5638be69ab3561854f34b before ad715e713610d2d5473c3a6498c825ccecf26491; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 708e87937de93f445225c134a2e20519f9b4ce60; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 18ef24cdb2eba32e38f1d27f2d02b7b4212e8f76; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 010eee265d6bd8769b6a523d2a0693d9b3f5df43; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 379d85c7f25f3e05a428225e6b8a65613c6e9b9d; from eaea34b23c46bf17b4a5638be69ab3561854f34b before e098d9cc8859614a7f7baebc96e32a5a16b18ed2; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 0ada54ea63e48b9c1608e917ccb7dfadbe86db28; from eaea34b23c46bf17b4a5638be69ab3561854f34b before 447c9303942c439a117d9b76ce6d6e2116b38ee7 | CNA record |
References
- https://git.kernel.org/stable/c/ad715e713610d2d5473c3a6498c825ccecf26491
- https://git.kernel.org/stable/c/708e87937de93f445225c134a2e20519f9b4ce60
- https://git.kernel.org/stable/c/18ef24cdb2eba32e38f1d27f2d02b7b4212e8f76
- https://git.kernel.org/stable/c/010eee265d6bd8769b6a523d2a0693d9b3f5df43
- https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d
- https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2
- https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28
- https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.