CVE-2026-23439

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2026-04-03. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
5.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.5Exploit: 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:

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n

When CONFIG_IPV6 is disabled, the udp_sock_create6() function returns 0 (success) without actually creating a socket. Callers such as fou_create() then proceed to dereference the uninitialized socket pointer, resulting in a NULL pointer dereference.

The captured NULL deref crash: BUG: kernel NULL pointer dereference, address: 0000000000000018 RIP: 0010:fou_nl_add_doit (net/ipv4/fou_core.c:590 net/ipv4/fou_core.c:764) [...] Call Trace: genl_family_rcv_msg_doit.constprop.0 (net/netlink/genetlink.c:1114) genl_rcv_msg (net/netlink/genetlink.c:1194 net/netlink/genetlink.c:1209) [...] netlink_rcv_skb (net/netlink/af_netlink.c:2550) genl_rcv (net/netlink/genetlink.c:1219) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sock_sendmsg (net/socket.c:727 (discriminator 1) net/socket.c:742 (discriminator 1)) __sys_sendto (./include/linux/file.h:62 (discriminator 1) ./include/linux/file.h:83 (discriminator 1) net/socket.c:2183 (discriminator 1)) __x64_sys_sendto (net/socket.c:2213 (discriminator 1) net/socket.c:2209 (discriminator 1) net/socket.c:2209 (discriminator 1)) do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) entry_SYSCALL_64_after_hwframe (net/arch/x86/entry/entry_64.S:130)

This patch makes udp_sock_create6 return -EPFNOSUPPORT instead, so callers correctly take their error paths. There is only one caller of the vulnerable function and only privileged users can trigger it.

CVSS v3
5.5
EG Score
5.5(medium)
EPSS
2.9%
KEV
Not listed

Published

April 3, 2026

Last Modified

July 14, 2026

Advisory Details (10)

Auto-updated Jul 17, 2026
⚠️ Active exploitation confirmed. No patch confirmed yet.
generic🔴 Active Exploitation

SSA-082556

https://cert-portal.siemens.com/productcert/html/ssa-082556.html
generic

SSA-019113

https://cert-portal.siemens.com/productcert/html/ssa-019113.html
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243f
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015d
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5e
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9
generic

udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9

Vendor Advisories for CVE-2026-23439(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
linuxKernel @ 5.10.253—osv

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 51× 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 113 total refreshes for this CVE.

  1. 2026-07-17 03:24 UTCOSV refresh
  2. 2026-07-16 17:03 UTCEPSS rescore
  3. 2026-07-16 17:03 UTCEPSS rescore
  4. 2026-07-15 16:57 UTCEPSS rescore
  5. 2026-07-15 16:57 UTCEPSS rescore
  6. 2026-07-15 02:00 UTCEPSS rescore
  7. 2026-07-15 02:00 UTCEPSS rescore
  8. 2026-07-14 13:19 UTCNVD updateCVSS v3 → 5.5 · severity → MEDIUM
  9. 2026-07-14 13:11 UTCMITRE cvelistV5
  10. 2026-07-13 22:30 UTCEPSS rescore
  11. 2026-07-13 06:13 UTCEPSS rescore
  12. 2026-07-13 06:13 UTCEPSS rescore
  13. 2026-07-12 05:46 UTCEPSS rescore
  14. 2026-07-12 05:46 UTCEPSS rescore
  15. 2026-07-11 08:27 UTCEPSS rescore
  16. 2026-07-09 19:10 UTCEPSS rescore
  17. 2026-07-08 15:15 UTCEPSS rescore
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  19. 2026-07-07 13:46 UTCEPSS rescore
  20. 2026-07-06 16:27 UTCEPSS rescore
  21. 2026-07-06 16:27 UTCEPSS rescore
  22. 2026-07-06 02:23 UTCEPSS rescore
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  24. 2026-07-05 02:30 UTCEPSS rescore
  25. 2026-07-04 06:31 UTCEPSS rescore
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  1. 2026-07-04 06:31 UTCEPSS rescore
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  4. 2026-06-30 23:22 UTCEPSS rescore
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  9. 2026-06-28 04:56 UTCEPSS rescore
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  11. 2026-06-27 03:08 UTCEPSS rescore
  12. 2026-06-25 13:49 UTCEPSS rescore
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  20. 2026-06-21 14:56 UTCEPSS rescore
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  22. 2026-06-21 01:59 UTCEPSS rescore
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  24. 2026-06-19 19:25 UTCEPSS rescore
  25. 2026-06-19 19:25 UTCEPSS rescore
  26. 2026-06-18 17:52 UTCEPSS rescore
  27. 2026-06-17 17:53 UTCEPSS rescore
  28. 2026-06-17 17:53 UTCEPSS rescore
  29. 2026-06-16 17:52 UTCEPSS rescore
  30. 2026-06-15 17:48 UTCEPSS rescore
  31. 2026-06-14 23:18 UTCEPSS rescore
  32. 2026-06-13 23:00 UTCEPSS rescore
  33. 2026-06-12 23:12 UTCEPSS rescore
  34. 2026-06-12 23:12 UTCEPSS rescore
  35. 2026-06-11 22:03 UTCGHSA enrichment
  36. 2026-06-11 14:00 UTCEPSS rescore
  37. 2026-06-10 22:18 UTCEPSS rescore
  38. 2026-06-10 13:38 UTCGHSA enrichment
  39. 2026-06-09 14:34 UTCGHSA enrichment
  40. 2026-06-08 14:17 UTCEPSS rescore
  41. 2026-06-08 14:17 UTCEPSS rescore
  42. 2026-06-08 08:45 UTCGHSA enrichment
  43. 2026-06-07 15:25 UTCEPSS rescore
  44. 2026-06-07 15:24 UTCEPSS rescore
  45. 2026-06-07 10:57 UTCGHSA enrichment
  46. 2026-06-06 13:47 UTCEPSS rescore
  47. 2026-06-06 13:47 UTCEPSS rescore
  48. 2026-06-06 13:47 UTCEPSS rescore
  49. 2026-06-05 22:47 UTCEPSS rescore
  50. 2026-06-05 06:10 UTCEPSS rescore
  51. 2026-06-05 06:10 UTCEPSS rescore
  52. 2026-06-04 13:12 UTCEPSS rescore
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  54. 2026-06-04 13:12 UTCEPSS rescore
  55. 2026-06-02 20:13 UTCEPSS rescore
  56. 2026-06-02 20:13 UTCEPSS rescore
  57. 2026-06-01 13:51 UTCEPSS rescore
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  59. 2026-06-01 13:51 UTCEPSS rescore
  60. 2026-05-31 22:30 UTCEPSS rescore
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  65. 2026-05-29 13:44 UTCEPSS rescore
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  75. 2026-05-26 07:18 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-23439?
CVE-2026-23439 is a medium vulnerability published on April 3, 2026. In the Linux kernel, the following vulnerability has been resolved: udptunnel: fix NULL deref caused by udpsockcreate6 when CONFIGIPV6=n When CONFIGIPV6 is disabled, the udpsock_create6() function returns 0 (success) without actually creating a socket. Callers such as fou_create() then proceed to…
When was CVE-2026-23439 disclosed?
CVE-2026-23439 was first published in the National Vulnerability Database on April 3, 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-2026-23439 actively exploited?
CVE-2026-23439 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-23439?
CVE-2026-23439 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-23439?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23439, 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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