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CVE-2026-81000— net: tun: bound receive headroom

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 4.6版本存在安全漏洞，该漏洞源于tun_get_user()使用tun->align作为skb头部空间和线性数据保留量时未正确限制接收头部空间，OVS可向TUN或TAP传播过大的headroom请求，导致SKB_MAX_HEAD(align)下溢并在转换为size_t时回绕，tun_alloc_skb()可能将skb->data放置在分配的头部之外，可能造成内存损坏。

CVSS 7.8 · High EPSS 0.36% · P28

Possible ATT&CK Techniques 1 AI

T1202 · Indirect Command Execution

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux eaea34b23c46bf17b4a5638be69ab3561854f34b< ad715e713610d2d5473c3a6498c825ccecf26491 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 708e87937de93f445225c134a2e20519f9b4ce60 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 18ef24cdb2eba32e38f1d27f2d02b7b4212e8f76 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 010eee265d6bd8769b6a523d2a0693d9b3f5df43 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 379d85c7f25f3e05a428225e6b8a65613c6e9b9d affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< e098d9cc8859614a7f7baebc96e32a5a16b18ed2 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 0ada54ea63e48b9c1608e917ccb7dfadbe86db28 affected
eaea34b23c46bf17b4a5638be69ab3561854f34b< 447c9303942c439a117d9b76ce6d6e2116b38ee7 affected
… +10 more rows
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I. Basic Information for CVE-2026-81000

Vulnerability Information
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Vulnerability Title
net: tun: bound receive headroom
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 4.6版本存在安全漏洞，该漏洞源于tun_get_user()使用tun->align作为skb头部空间和线性数据保留量时未正确限制接收头部空间，OVS可向TUN或TAP传播过大的headroom请求，导致SKB_MAX_HEAD(align)下溢并在转换为size_t时回绕，tun_alloc_skb()可能将skb->data放置在分配的头部之外，可能造成内存损坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux eaea34b23c46bf17b4a5638be69ab3561854f34b ~ ad715e713610d2d5473c3a6498c825ccecf26491 -
Linux Linux 4.6 -

II. Public POCs for CVE-2026-81000

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III. Intelligence Information for CVE-2026-81000

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Patches & Fixes for CVE-2026-81000 (8)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89656 9.8 CRITICAL libceph: reject buckets with mismatched CRUSH ids
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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