CVE-2026-52940

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2026-06-24. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.5Exploit: None knownExposed: 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:

tun: zero the whole vnet header in tun_put_user()

tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb() only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)), leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack garbage.

An unprivileged user can set the vnet header size to 24 with TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the partially-initialized struct to userspace, leaking 14 bytes of kernel stack on every read of a non-tunnel packet.

Fix it the same way tun_get_user() already does by zeroing the whole header right after declaration.

CVSS v3
5.5
EG Score
5.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
5%
KEV
Not listed

Published

June 24, 2026

Last Modified

July 8, 2026

Advisory Details (3)

Auto-updated Jul 8, 2026
No patch confirmed yet.
generic

tun: zero the whole vnet header in tun_put_user() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d
generic

tun: zero the whole vnet header in tun_put_user() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5
generic

tun: zero the whole vnet header in tun_put_user() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380

Vendor Advisories for CVE-2026-52940(1)

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

Affected Packages

(1 across 1 ecosystem)
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 7.0.9-1~bpo13+1 (145 versions)7.0.13-1—

Data Freshness Timeline

(refreshed 4× in last 7d / 49× 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.

Showing the most recent 100 of 152 total refreshes for this CVE.

  1. 2026-09-10 09:35 UTCEPSS rescore
  2. 2026-09-08 22:01 UTCEPSS rescore
  3. 2026-09-07 16:01 UTCEPSS rescore
  4. 2026-09-06 13:47 UTCEPSS rescore
  5. 2026-09-04 05:06 UTCEPSS rescore
  6. 2026-09-02 14:12 UTCEPSS rescore
  7. 2026-09-01 13:54 UTCEPSS rescore
  8. 2026-09-01 04:40 UTCEPSS rescore
  9. 2026-08-30 20:21 UTCEG score recompute
  10. 2026-08-30 20:21 UTCGHSA enrichment
  11. 2026-08-30 19:17 UTCEPSS rescore
  12. 2026-08-30 01:22 UTCEPSS rescore
  13. 2026-08-28 21:41 UTCEPSS rescore
  14. 2026-08-28 04:52 UTCEG score recompute
  15. 2026-08-28 04:52 UTCGHSA enrichment
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-26 14:46 UTCEPSS rescore
  18. 2026-08-25 13:49 UTCEPSS rescore
  19. 2026-08-24 13:50 UTCEG score recompute
  20. 2026-08-24 13:50 UTCGHSA enrichment
  21. 2026-08-23 11:57 UTCEG score recompute
  22. 2026-08-23 11:57 UTCGHSA enrichment
  23. 2026-08-23 00:19 UTCEPSS rescore
  24. 2026-08-22 13:20 UTCEG score recompute
  25. 2026-08-22 13:20 UTCGHSA enrichment
Show 75 more
  1. 2026-08-21 23:49 UTCEPSS rescore
  2. 2026-08-21 06:14 UTCEG score recompute
  3. 2026-08-21 06:14 UTCGHSA enrichment
  4. 2026-08-20 22:55 UTCEPSS rescore
  5. 2026-08-20 07:36 UTCEG score recompute
  6. 2026-08-20 07:36 UTCGHSA enrichment
  7. 2026-08-19 17:04 UTCEPSS rescore
  8. 2026-08-19 02:22 UTCEG score recompute
  9. 2026-08-19 02:22 UTCGHSA enrichment
  10. 2026-08-18 13:48 UTCEPSS rescore
  11. 2026-08-17 13:47 UTCEPSS rescore
  12. 2026-08-17 00:49 UTCEG score recompute
  13. 2026-08-17 00:49 UTCGHSA enrichment
  14. 2026-08-16 14:56 UTCEPSS rescore
  15. 2026-08-16 02:14 UTCEPSS rescore
  16. 2026-08-16 02:12 UTCGHSA enrichment
  17. 2026-08-15 03:35 UTCEG score recompute
  18. 2026-08-15 03:35 UTCGHSA enrichment
  19. 2026-08-15 01:30 UTCEPSS rescore
  20. 2026-08-14 04:57 UTCEG score recompute
  21. 2026-08-14 04:57 UTCGHSA enrichment
  22. 2026-08-13 22:00 UTCEPSS rescore
  23. 2026-08-13 06:20 UTCEG score recompute
  24. 2026-08-13 06:20 UTCGHSA enrichment
  25. 2026-08-12 13:51 UTCEPSS rescore
  26. 2026-08-12 07:43 UTCEG score recompute
  27. 2026-08-12 07:43 UTCGHSA enrichment
  28. 2026-08-11 09:06 UTCEG score recompute
  29. 2026-08-11 09:06 UTCGHSA enrichment
  30. 2026-08-11 00:00 UTCEPSS rescore
  31. 2026-08-10 10:29 UTCGHSA enrichment
  32. 2026-08-09 11:52 UTCEG score recompute
  33. 2026-08-09 11:52 UTCGHSA enrichment
  34. 2026-08-08 16:37 UTCEPSS rescore
  35. 2026-08-08 13:15 UTCEG score recompute
  36. 2026-08-08 13:15 UTCGHSA enrichment
  37. 2026-08-07 14:37 UTCGHSA enrichment
  38. 2026-08-06 16:00 UTCEG score recompute
  39. 2026-08-06 16:00 UTCGHSA enrichment
  40. 2026-08-06 13:47 UTCEPSS rescore
  41. 2026-08-05 19:17 UTCEPSS rescore
  42. 2026-08-05 17:23 UTCGHSA enrichment
  43. 2026-08-04 18:30 UTCEG score recompute
  44. 2026-08-04 18:29 UTCGHSA enrichment
  45. 2026-08-04 15:10 UTCEPSS rescore
  46. 2026-08-04 10:39 UTCEPSS rescore
  47. 2026-08-03 19:43 UTCEG score recompute
  48. 2026-08-03 19:43 UTCGHSA enrichment
  49. 2026-08-03 10:36 UTCEPSS rescore
  50. 2026-08-02 21:06 UTCEG score recompute
  51. 2026-08-02 21:06 UTCGHSA enrichment
  52. 2026-08-02 02:27 UTCEPSS rescore
  53. 2026-08-01 22:29 UTCEG score recompute
  54. 2026-08-01 22:29 UTCGHSA enrichment
  55. 2026-08-01 04:16 UTCEPSS rescore
  56. 2026-07-31 23:52 UTCGHSA enrichment
  57. 2026-07-31 01:11 UTCEG score recompute
  58. 2026-07-31 01:11 UTCGHSA enrichment
  59. 2026-07-30 16:28 UTCEPSS rescore
  60. 2026-07-30 02:30 UTCEG score recompute
  61. 2026-07-30 02:30 UTCGHSA enrichment
  62. 2026-07-30 01:30 UTCEPSS rescore
  63. 2026-07-29 01:05 UTCEG score recompute
  64. 2026-07-29 01:05 UTCGHSA enrichment
  65. 2026-07-28 15:37 UTCEPSS rescore
  66. 2026-07-27 17:42 UTCGHSA enrichment
  67. 2026-07-26 15:44 UTCEG score recompute
  68. 2026-07-26 15:44 UTCGHSA enrichment
  69. 2026-07-26 14:54 UTCEPSS rescore
  70. 2026-07-25 14:18 UTCEPSS rescore
  71. 2026-07-24 14:18 UTCEPSS rescore
  72. 2026-07-23 14:18 UTCEPSS rescore
  73. 2026-07-23 03:19 UTCEG score recompute
  74. 2026-07-22 14:08 UTCEPSS rescore
  75. 2026-07-19 14:31 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-52940?
CVE-2026-52940 is a medium vulnerability published on June 24, 2026. In the Linux kernel, the following vulnerability has been resolved: tun: zero the whole vnet header in tunputuser() tunputuser() declares an on-stack struct virtionethdrv1hash_tunnel without zeroing it. For a non-tunnel skb, virtionethdrtnlfrom_skb() only initializes the first 10 bytes…
When was CVE-2026-52940 disclosed?
CVE-2026-52940 was first published in the National Vulnerability Database on June 24, 2026, with the most recent update on July 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-52940 actively exploited?
CVE-2026-52940 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 94.5% of all scored CVEs.
What is the CVSS score of CVE-2026-52940?
CVE-2026-52940 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-52940?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-52940, 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.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-52940

Explore →

Is Your Infrastructure Affected by CVE-2026-52940?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs