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NVD / CVE Program· CNA Linux

CVE-2026-68377: net/sched: act_tunnel_key: Defer dst_release to RCU callback

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.12% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 2200a00ff247f70f5dcdb4e6f14b0d48ddac5467, 2791a501da508b704a617b4dba29db54a65bc9f7, 389d03992dabb80488228e8119b9dd6d0f58e1a6; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 2200a00ff247f70f5dcdb4e6f14b0d48ddac5467, 2791a501da508b704a617b4dba29db54a65bc9f7, 389d03992dabb80488228e8119b9dd6d0f58e1a6; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_tunnel_key: Defer dst_release to RCU callback Fix a race-condition use-after-free in tunnel_key_release_params(). The function releases the metadata_dst of the old params synchronously via dst_release() while deferring the params struct free with kfree_rcu(). A concurrent tunnel_key_act() reader on the datapath may still hold the old params pointer (under rcu_read_lock_bh) and proceed to call dst_clone(&params->tcft_enc_metadata->dst) after the writer's dst_release has already pushed the dst's rcuref to RCUREF_DEAD. zdi-disclosures@trendmicro.com produced a poc which i (and Victor) verified that KASAN reports: ================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 BUG: KASAN: slab-use-after-free in atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326 BUG: KASAN: slab-use-after-free in __rcuref_put include/linux/rcuref.h:109 BUG: KASAN: slab-use-after-free in rcuref_put include/linux/rcuref.h:173 BUG: KASAN: slab-use-after-free in dst_release+0x5b/0x370 net/core/dst.c:168 Write of size 4 at addr ffff88806158de40 by task poc/9388 CPU: 0 UID: 0 PID: 9388 Comm: poc Tainted: G W 7.1.0-rc7 #7 PREEMPT(lazy) Tainted: [W]=WARN Hardware name: QEMU Ubuntu 25.10 PC v2 (i440FX + PIIX, + 10.1 machine, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 print_report+0x139/0x4ad mm/kasan/report.c:482 kasan_report+0xe4/0x1d0 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 kasan_check_range+0x125/0x200 mm/kasan/generic.c:200 instrument_atomic_read_write include/linux/instrumented.h:112 atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326 __rcuref_put include/linux/rcuref.h:109 rcuref_put include/linux/rcuref.h:173 dst_release+0x5b/0x370 net/core/dst.c:168 refdst_drop include/net/dst.h:272 skb_dst_drop include/net/dst.h:284 skb_release_head_state+0x293/0x400 net/core/skbuff.c:1163 skb_release_all net/core/skbuff.c:1187 [..] Allocated by task 9391: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 __do_kmalloc_node mm/slub.c:5296 __kmalloc_noprof+0x2f1/0x830 mm/slub.c:5308 kmalloc_noprof include/linux/slab.h:954 kzalloc_noprof include/linux/slab.h:1188 offload_action_alloc+0x2f/0x130 net/core/flow_offload.c:35 tcf_action_offload_add_ex+0x1ba/0x880 net/sched/act_api.c:258 tcf_action_offload_add net/sched/act_api.c:293 tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547 tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101 [..] Freed by task 9391: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 __kasan_slab_free+0x6b/0x90 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 slab_free_hook mm/slub.c:2689 slab_free mm/slub.c:6251 kfree+0x21f/0x6b0 mm/slub.c:6566 tcf_action_offload_add_ex+0x4ad/0x880 net/sched/act_api.c:284 tcf_action_offload_add net/sched/act_api.c:293 tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547 tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101 The buggy address belongs to the object at ffff88806158de00 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 64 bytes inside of freed 256-byte region [ffff88806158de00, ffff88806158df00) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88806158d600 pfn:0x6158c head: order:1 mapcount:0 entire_map ---truncated---

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Aug 10, 2026
Updated
Oct 19, 2026
EPSS
0.1% · 2th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 02239e797ac75f89a05622a27d04695f08c1ca89, ca9b7a65a2c97579fcdd509d454d48e3a5c49af8, 5.0affected
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before b5931f020b681fdcb9378262d89b61cb3c7ebbf8affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before 389d03992dabb80488228e8119b9dd6d0f58e1a6affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before 676ad6aa7cec89a08d2a5ce3cd5959e313f29733affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before 531dbb5bb98e52ad26be7e90f9f8bec707c5bd0eaffected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before 2200a00ff247f70f5dcdb4e6f14b0d48ddac5467affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before fed1b1ddab41a0e7a462ac690a0c8af6ff793624affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before 2791a501da508b704a617b4dba29db54a65bc9f7affected · git
    • 9174c3df1cd181c14913138d50ccbe539bb08335 and later · before f1f5c8a3955f8fda3f84ed883ac8daa1847e724caffected · git
    • 4.19.19 and later · before 4.20affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-68375Aug 10, 2026 · bnxt_en: Handle partially initialized auxiliary devices
    0Monitor
  • ← EarlierCVE-2026-68376Aug 10, 2026 · sctp: fix auth_hmacs array size in struct sctp_cookie
    32Monitor
  • Later →CVE-2026-68381Aug 10, 2026 · ksmbd: pin conn during async oplock break notification
    39Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2200a00ff247f70f5dcdb4e6f14b0d48ddac5467Vendor (CNA)
Linux Linux2791a501da508b704a617b4dba29db54a65bc9f7Vendor (CNA)
Linux Linux389d03992dabb80488228e8119b9dd6d0f58e1a6Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux4.21Vendor (CNA)
Linux Linux531dbb5bb98e52ad26be7e90f9f8bec707c5bd0eVendor (CNA)
Linux Linux676ad6aa7cec89a08d2a5ce3cd5959e313f29733Vendor (CNA)
Linux Linuxb5931f020b681fdcb9378262d89b61cb3c7ebbf8Vendor (CNA)
Linux Linuxf1f5c8a3955f8fda3f84ed883ac8daa1847e724cVendor (CNA)
Linux Linuxfed1b1ddab41a0e7a462ac690a0c8af6ff793624Vendor (CNA)
azl3 kernel 6.6.143.1-1 on Azure Linux 3.06.6.150.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.58.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)

+21

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-681170 days aparttipc: clear sock->sk on the failed-insert path in tipc_sk_create()
    39Monitor
  • CVE-2026-681270 days apartila: reload IPv6 header after pskb_may_pull in checksum adjust
    39Monitor
  • CVE-2026-681440 days apartphonet: pep: fix use-after-free in pep_get_sb()
    39Monitor
  • CVE-2026-681560 days apartlibceph: refresh auth->authorizer_buf{,_len} after authorizer update
    39Monitor
  • CVE-2026-683810 days apartksmbd: pin conn during async oplock break notification
    39Monitor
  • CVE-2026-684260 days apartxfrm: fix stale skb->prev after async crypto steals a GSO segment
    39Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records