CVE-2026-23340

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-03-25. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs

When shrinking the number of real tx queues, netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush qdiscs for queues which will no longer be used.

qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with qdisc_lock(). However, for lockless qdiscs, the dequeue path is serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so qdisc_reset() can run concurrently with __qdisc_run() and free skbs while they are still being dequeued, leading to UAF.

This can easily be reproduced on e.g. virtio-net by imposing heavy traffic while frequently changing the number of queue pairs:

iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done

With KASAN enabled, this leads to reports like:

BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760 ... Call Trace: ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ...

Allocated by task 1270 on cpu 5 at 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ...

Freed by task 1306 on cpu 3 at 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ...

Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the serialization model already used by dev_reset_queue().

Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state reflects an empty queue, avoiding needless re-scheduling.

CVSS v3
7.8
EG Score
7.8(medium)
EPSS
3.5%
KEV
Not listed

Published

March 25, 2026

Last Modified

July 14, 2026

Advisory Details (7)

Auto-updated Jun 10, 2026
No patch confirmed yet.
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/c69df4e0524f8de8e176ba389acd83e85f5f49d0
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7f083faf59d14c04e01ec05a7507f036c965acf8
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7594467c49bfc2f4644dee0415ac2290db11fa0d
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5bc4e69306ed7ae02232eb4c0b23ed621a26d504
generic

net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5bb27ad54d12de67e457d7d251198e361bef835e

Vendor Advisories for CVE-2026-23340(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 0× in last 7d / 0× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-15 16:57 UTCEPSS rescore
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  25. 2026-06-29 05:02 UTCOSV refresh
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  1. 2026-06-28 14:07 UTCEPSS rescore
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  3. 2026-06-28 04:56 UTCEPSS rescore
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  29. 2026-06-11 23:32 UTCEG score recompute
  30. 2026-06-11 23:32 UTCVendor advisory
  31. 2026-06-11 23:32 UTCGHSA enrichment
  32. 2026-06-11 14:00 UTCEPSS rescore
  33. 2026-06-10 22:18 UTCEPSS rescore
  34. 2026-06-10 17:45 UTCEG score recompute
  35. 2026-06-10 17:45 UTCVendor advisory
  36. 2026-06-10 17:45 UTCGHSA enrichment
  37. 2026-06-10 13:22 UTCEPSS rescore
  38. 2026-06-10 05:26 UTCEG score recompute
  39. 2026-06-10 05:26 UTCVendor advisory
  40. 2026-06-10 05:26 UTCGHSA enrichment
  41. 2026-06-09 15:56 UTCEG score recompute
  42. 2026-06-09 15:56 UTCVendor advisory
  43. 2026-06-09 15:56 UTCGHSA enrichment
  44. 2026-06-08 14:32 UTCEG score recompute
  45. 2026-06-08 14:32 UTCVendor advisory
  46. 2026-06-08 14:32 UTCGHSA enrichment
  47. 2026-06-08 14:17 UTCEPSS rescore
  48. 2026-06-08 14:17 UTCEPSS rescore
  49. 2026-06-08 01:07 UTCEG score recompute
  50. 2026-06-08 01:07 UTCVendor advisory
  51. 2026-06-08 01:07 UTCGHSA enrichment
  52. 2026-06-07 15:25 UTCEPSS rescore
  53. 2026-06-07 15:24 UTCEPSS rescore
  54. 2026-06-07 12:33 UTCEG score recompute
  55. 2026-06-07 12:33 UTCVendor advisory
  56. 2026-06-07 12:33 UTCGHSA enrichment
  57. 2026-06-06 13:47 UTCEPSS rescore
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  71. 2026-06-01 07:13 UTCOSV refresh
  72. 2026-05-31 22:30 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2026-23340?
CVE-2026-23340 is a high vulnerability published on March 25, 2026. In the Linux kernel, the following vulnerability has been resolved: net: sched: avoid qdiscresetalltxgt() vs dequeue race for lockless qdiscs When shrinking the number of real tx queues, netifsetrealnumtxqueues() calls qdiscresetalltx_gt() to flush qdiscs for queues which will no longer be used.…
When was CVE-2026-23340 disclosed?
CVE-2026-23340 was first published in the National Vulnerability Database on March 25, 2026, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-23340 actively exploited?
CVE-2026-23340 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-23340?
CVE-2026-23340 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-23340?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23340, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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