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CVE Record

CVE-2026-23011: ipv4: ip_gre: make ipgre_header() robust

In the Linux kernel, the following vulnerability has been resolved: ipv4: ip_gre: make ipgre_header() robust Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust") Over the years, syzbot found many ways to crash the kernel in ipgre_header() [1]. This involves team or bonding drivers ability to dynamically change their dev->needed_headroom and/or dev->hard_header_len In this particular crash mld_newpack() allocated an skb with a too small reserve/headroom, and by the time mld_sendpack() was called, syzbot managed to attach an ipgre device. [1] skbuff: skb_under_panic: text:ffffffff89ea3cb7 len:2030915468 put:2030915372 head:ffff888058b43000 data:ffff887fdfa6e194 tail:0x120 end:0x6c0 dev:team0 kernel BUG at net/core/skbuff.c:213 ! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 1322 Comm: kworker/1:9 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: mld mld_ifc_work RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:213 Call Trace: <TASK> skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ipgre_header+0x67/0x290 net/ipv4/ip_gre.c:897 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2026-23011 is a Linux kernel crash bug in GRE tunneling header handling. The public record describes syzbot-triggered kernel BUG crashes when network device headroom or header length changes dynamically. Business impact is mainly availability risk on exposed Linux systems, but the record does not provide CVSS, confirmed exploitation, or product-specific impact details.

Executive priority

Monitor and patch through normal kernel maintenance unless GRE plus team or bonding is used in production. Raise priority where a kernel crash would affect critical network services or appliances. No source confirms active exploitation or severity scoring.

Technical view

The issue is in ipv4 ip_gre ipgre_header(). A too-small skb reserve/headroom can reach skb_push(), causing skb_under_panic and a kernel BUG. The described crash involves MLD packet processing, team or bonding drivers changing needed_headroom or hard_header_len, and attachment of an ipgre device before send.

Likely exposure

Likely exposure is Linux systems using or able to load GRE tunneling with team or bonding networking. The source lists Linux kernel versions and stable commits, but version boundaries are not fully explained in the bundle. Embedded Linux products may need vendor confirmation.

Exploitation context

The evidence shows syzbot crash discovery and kernel fix references. The bundle says KEV is false and provides no cited evidence of active exploitation. Treat this as a potential denial-of-service condition until vendor advisories or distribution notices clarify reachability and prerequisites.

Researcher notes

Key uncertainty is exploitability outside syzbot conditions. The record describes a robustness fix analogous to an earlier ip6_gre change and a crash path through skb_push(). Avoid assuming remote reachability without testing vendor kernels and exact network prerequisites.

Mitigation direction

  • Check your Linux distribution or vendor advisory for fixed kernel packages.
  • Prioritize kernels using GRE with team or bonding networking.
  • Apply the relevant stable kernel update when available for your branch.
  • If patching is delayed, review whether GRE, team, or bonding are required.
  • Track downstream vendor advisories for embedded Linux products.

Validation and detection

  • Inventory kernel versions and enabled GRE, team, and bonding modules.
  • Compare running kernels with vendor-fixed package versions or listed stable commits.
  • Review network configurations for ip_gre devices with team or bonding interfaces.
  • Check logs for kernel BUG, skb_under_panic, or ipgre_header crashes.
  • Confirm vendor advisories for any appliance or embedded Linux exposure.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2026-23011 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxc54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5, c54419321455631079c7d6e60bc732dd0c5914c5unaffected
LinuxLinux3.10, 0, 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.67, 6.18.7, 6.19affected
Weakness

CWE details

No CWE listed

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