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CVE-2026-89563— ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()

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 4.7版本存在安全漏洞，该漏洞源于ip6_tnl_xmit()中使用skb_realloc_headroom()扩展headroom后，后续错误路径中调用者可能释放已消耗的skb，导致释放后重用。

CVSS 7.8 · High EPSS 0.14% · P3

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 058214a4d1dfefed9f01a277fadd3590acb5f990< 6e8eff8ed13b14708bc39f170144eacde494aac6 affected
058214a4d1dfefed9f01a277fadd3590acb5f990< dc1a319a4815c074914e2812e0e9cd0164ca682b affected
058214a4d1dfefed9f01a277fadd3590acb5f990< 629d5557e635cdbc109a14ed913ba5a540e3f79a affected
058214a4d1dfefed9f01a277fadd3590acb5f990< defa0adeff132cc90ed66915b9a104d9393e1e54 affected
058214a4d1dfefed9f01a277fadd3590acb5f990< 37df5bc6b5ccad88c2faa0f5466f150178882b74 affected
058214a4d1dfefed9f01a277fadd3590acb5f990< b36dfd6e8cff00cea81c11cc0af88d1564763461 affected
058214a4d1dfefed9f01a277fadd3590acb5f990< 8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52 affected
058214a4d1dfefed9f01a277fadd3590acb5f990< 87f21b59ddc618eff9670c174842964ad65fdade affected
… +10 more rows
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I. Basic Information for CVE-2026-89563

Vulnerability Information
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Vulnerability Title
ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit() ip6_tnl_xmit() may need to expand headroom before it can push the outer IPv6 and optional encap headers. It currently does that with skb_realloc_headroom(), copies skb->sk ownership, consumes the original skb, and then continues processing with the replacement skb kept only in its local variable. That is safe only if the helper cannot fail afterwards. But this helper still has post-reallocation error exits. collect_md tunnels reject non-NONE encap after the replacement, and ip6_tnl_encap() can also fail later. In those cases the helper returns an error to its callers while the caller still only has the original skb pointer. Both ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on error, so they can end up freeing an skb that ip6_tnl_xmit() already consumed. Use skb_cow_head() instead. It provides the required headroom and writability without privately replacing the caller-owned skb, so later error returns cannot leave callers with a stale pointer. The Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING and already call skb_cow_head() before entering ip6_tnl_xmit(). They do not rely on the removed skb_shared() reallocation. This also makes the IPv6 tunnel path consistent with ip_tunnel_xmit().
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 4.7版本存在安全漏洞，该漏洞源于ip6_tnl_xmit()中使用skb_realloc_headroom()扩展headroom后，后续错误路径中调用者可能释放已消耗的skb，导致释放后重用。
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 058214a4d1dfefed9f01a277fadd3590acb5f990 ~ 6e8eff8ed13b14708bc39f170144eacde494aac6 -
Linux Linux 4.7 -

II. Public POCs for CVE-2026-89563

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III. Intelligence Information for CVE-2026-89563

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Patches & Fixes for CVE-2026-89563 (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-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
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

V. Comments for CVE-2026-89563

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