VulnerabilityPublished 10 Aug 2026Updated 6 Nov 2026

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

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in 675ed582c1aa4d919dd535490de08c015005c653 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 17:04 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in 675ed582c1aa4d919dd535490de08c015005c653, 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3, 9f948e9aede9678f4103457daf2bc9dd54c65a06 +1

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to 675ed582c1aa4d919dd535490de08c015005c653, 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3, 9f948e9aede9678f4103457daf2bc9dd54c65a06 or 2bffe379023512d280337c70faeb6a8cc435db5e.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383, < 675ed582c1aa4d919dd535490de08c015005c653	Fixed in 675ed582c1aa4d919dd535490de08c015005c653
LinuxLinux	Affected ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383, < 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3	Fixed in 15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3
LinuxLinux	Affected ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383, < 9f948e9aede9678f4103457daf2bc9dd54c65a06	Fixed in 9f948e9aede9678f4103457daf2bc9dd54c65a06
LinuxLinux	Affected ≥ 00d066a4d4edbe559ba6c35153da71d4b2b8a383, < 2bffe379023512d280337c70faeb6a8cc435db5e	Fixed in 2bffe379023512d280337c70faeb6a8cc435db5e
LinuxLinux	Affected =6.12	Fixed in–

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.

References

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