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CVE-2026-68296— net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM

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 6.12版本存在安全漏洞，该漏洞源于GRE隧道中dev->lltx标志设置位置错误，可能导致GRE/GRETAP/ip6gre隧道在设置SEQ或CSUM+encap时失去无锁传输，存在ABBA死锁风险。

AI Predicted 4.3 Difficulty: Moderate EPSS 0.20% · P10

Possible ATT&CK Techniques 1 AI

T1205.001 · Port Knocking

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 00d066a4d4edbe559ba6c35153da71d4b2b8a383< 9f948e9aede9678f4103457daf2bc9dd54c65a06 affected
00d066a4d4edbe559ba6c35153da71d4b2b8a383< 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3 affected
00d066a4d4edbe559ba6c35153da71d4b2b8a383< 2bffe379023512d280337c70faeb6a8cc435db5e affected
00d066a4d4edbe559ba6c35153da71d4b2b8a383< 675ed582c1aa4d919dd535490de08c015005c653 affected
6.12 affected
< 6.12 unaffected
6.12.101≤ 6.12.* unaffected
6.18.42≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-68296

Vulnerability Information
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Vulnerability Title
net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM Before commit 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx"), NETIF_F_LLTX was set unconditionally in both __gre_tunnel_init() and ip6gre_tnl_init_features() alongside GRE_FEATURES: dev->features |= GRE_FEATURES | NETIF_F_LLTX; When that commit converted NETIF_F_LLTX to the dev->lltx flag, it placed 'dev->lltx = true' after the SEQ/CSUM early returns instead of before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or CSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition around their ndo_start_xmit. Since GRE xmit re-enters the stack via ip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the underlay device. CPU0 CPU1 ---- ---- lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); Fix by moving dev->lltx = true before the early returns in both functions, restoring the original unconditional behavior.
Source: CVE Program / CVE List V5
CVSS Information
N/A
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 6.12版本存在安全漏洞，该漏洞源于GRE隧道中dev->lltx标志设置位置错误，可能导致GRE/GRETAP/ip6gre隧道在设置SEQ或CSUM+encap时失去无锁传输，存在ABBA死锁风险。
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 00d066a4d4edbe559ba6c35153da71d4b2b8a383 ~ 9f948e9aede9678f4103457daf2bc9dd54c65a06 -
Linux Linux 6.12 -

II. Public POCs for CVE-2026-68296

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III. Intelligence Information for CVE-2026-68296

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Patches & Fixes for CVE-2026-68296 (2)

Same Patch Batch · Linux · 2026-08-10 · 344 CVEs total

CVE-2026-68161 9.8 CRITICAL sctp: close UDP tunnel sockets during netns teardown
CVE-2026-68123 9.8 CRITICAL openvswitch: fix GSO userspace truncation underflow
CVE-2026-68127 9.8 CRITICAL ila: reload IPv6 header after pskb_may_pull in checksum adjust
CVE-2026-68117 9.8 CRITICAL tipc: clear sock->sk on the failed-insert path in tipc_sk_create()
CVE-2026-68136 9.8 CRITICAL net: gro: fix double aggregation of flush-marked skbs
CVE-2026-68137 9.8 CRITICAL net/x25: fix use-after-free in x25_kill_by_neigh()
CVE-2026-68300 9.8 CRITICAL sctp: auth: verify auth requirement when auth_chunk is NULL
CVE-2026-68144 9.8 CRITICAL phonet: pep: fix use-after-free in pep_get_sb()
CVE-2026-68154 9.8 CRITICAL libceph: reject zero bucket types in crush_decode
CVE-2026-68156 9.8 CRITICAL libceph: refresh auth->authorizer_buf{,_len} after authorizer update
CVE-2026-68158 9.8 CRITICAL libceph: Fix multiplication overflow in decode_new_up_state_weight()
CVE-2026-68159 9.8 CRITICAL libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE
CVE-2026-68160 9.8 CRITICAL ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()
CVE-2026-68302 9.8 CRITICAL amt: re-read skb header pointers after every pull
CVE-2026-68170 9.8 CRITICAL mptcp: fix stale skb->sk reference on subflow close
CVE-2026-68426 9.8 CRITICAL xfrm: fix stale skb->prev after async crypto steals a GSO segment
CVE-2026-68388 9.8 CRITICAL smb/client: handle overlapping allocated ranges in fallocate
CVE-2026-68385 9.8 CRITICAL s390/checksum: Fix csum_partial() without vector facility
CVE-2026-68381 9.8 CRITICAL ksmbd: pin conn during async oplock break notification
CVE-2026-68124 9.6 CRITICAL mctp: serial: handle zero-length frames to prevent rx buffer overflow

Showing top 20 of 344 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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