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CVE Record

CVE-2026-31406: xfrm: Fix work re-schedule after cancel in xfrm_nat_keepalive_net_fini()

In the Linux kernel, the following vulnerability has been resolved: xfrm: Fix work re-schedule after cancel in xfrm_nat_keepalive_net_fini() After cancel_delayed_work_sync() is called from xfrm_nat_keepalive_net_fini(), xfrm_state_fini() flushes remaining states via __xfrm_state_delete(), which calls xfrm_nat_keepalive_state_updated() to re-schedule nat_keepalive_work. The following is a simple race scenario: cpu0 cpu1 cleanup_net() [Round 1] ops_undo_list() xfrm_net_exit() xfrm_nat_keepalive_net_fini() cancel_delayed_work_sync(nat_keepalive_work); xfrm_state_fini() xfrm_state_flush() xfrm_state_delete(x) __xfrm_state_delete(x) xfrm_nat_keepalive_state_updated(x) schedule_delayed_work(nat_keepalive_work); rcu_barrier(); net_complete_free(); net_passive_dec(net); llist_add(&net->defer_free_list, &defer_free_list); cleanup_net() [Round 2] rcu_barrier(); net_complete_free() kmem_cache_free(net_cachep, net); nat_keepalive_work() // on freed net To prevent this, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync().

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel race can leave delayed XFRM NAT keepalive work running after its network object is freed. A local, low-privileged attacker may be able to trigger memory corruption, potentially compromising confidentiality, integrity, and availability. Systems using affected kernels with IPsec/XFRM networking or frequent network-namespace teardown deserve prompt review.

Executive priority

Treat as a high-priority kernel update for exposed Linux infrastructure, especially VPN gateways, container platforms, and shared systems. The required local privileges reduce urgency below an unauthenticated remote flaw, but kernel-level confidentiality, integrity, and availability impact warrants timely patching. Escalate systems where untrusted users or workloads can influence network namespaces.

Technical view

During network-namespace cleanup, cancel_delayed_work_sync() can complete before XFRM state deletion schedules nat_keepalive_work again. That work may later dereference the freed network object, creating a use-after-free condition. The upstream correction uses disable_delayed_work_sync() to prevent rescheduling. CVSS 3.1 is 7.8: local access, low complexity, low privileges, no user interaction.

Likely exposure

Exposure requires an affected Linux kernel and access to the vulnerable XFRM NAT keepalive cleanup path. Risk is likely higher on IPsec/NAT-T systems and environments that create and destroy network namespaces. The supplied affected-version data is insufficiently structured to establish reliable fixed-version boundaries; verify distribution packages against vendor advisories and referenced commits.

Exploitation context

The supplied record does not establish active exploitation, and CVE-2026-31406 is not listed as KEV in the bundle. The CVSS vector indicates local, low-privileged access rather than remote exploitation. Successful exploitation could potentially produce kernel memory corruption, crashes, or privilege-impacting compromise, but no working exploit evidence is provided.

Researcher notes

This is a delayed-work lifecycle race producing a potential use-after-free during XFRM network teardown. The bundle provides four stable-kernel commits but does not map them cleanly to release branches or demonstrate exploitability. Researchers should validate branch-specific ancestry, configuration prerequisites, reachable namespace teardown paths, and whether vendor backports contain the semantic fix.

Mitigation direction

  • Update to a vendor-supported kernel containing the referenced delayed-work disable fix.
  • Confirm the updated kernel is active after installation and any required reboot.
  • Prioritize IPsec, NAT-T, container, and network-namespace hosts for remediation.
  • If updates are unavailable, obtain product-specific mitigations directly from the Linux distribution vendor.

Validation and detection

  • Inventory running kernel versions across Linux hosts, not merely installed package versions.
  • Compare each kernel package with its distribution advisory and the referenced stable commits.
  • Check whether hosts use XFRM, IPsec NAT-T, or frequent network-namespace teardown.
  • Verify the vendor kernel source includes disable_delayed_work_sync() in xfrm_nat_keepalive_net_fini().
  • After remediation, confirm systems booted the fixed kernel and retired vulnerable kernel packages.
Prepared
Confidence
medium
Sources
6

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

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CVE-2026-31406 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

1CVSS vectors
3Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2026-31406Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf531d13bdfe3f4f084aaa8acae2cb0f02295f5ae, f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae, f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae, f531d13bdfe3f4f084aaa8acae2cb0f02295f5aeunaffected
LinuxLinux6.11, 0, 6.12.80, 6.18.21, 6.19.11, 7.0affected
Weakness

CWE details

No CWE listed

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