CVE-2026-23300

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2026-03-25. 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:

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop

When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics.

Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows:

  • Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"):
RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change.
  • Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"):
RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless.
  • Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"):
RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_pcpu_rth_output is properly allocated, fixing the crash when IPv4 routes reference this nexthop.

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
3%
KEV
Not listed

Published

March 25, 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

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644
generic

net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093

Vendor Advisories for CVE-2026-23300(2)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
linuxKernel @ 5.10.253—osv
linuxKernel @ 6.1.167—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 6× in last 7d / 46× 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 143 total refreshes for this CVE.

  1. 2026-07-30 01:30 UTCEPSS rescore
  2. 2026-07-27 14:13 UTCEPSS rescore
  3. 2026-07-26 14:54 UTCEPSS rescore
  4. 2026-07-26 14:54 UTCEPSS rescore
  5. 2026-07-25 14:17 UTCEPSS rescore
  6. 2026-07-25 14:17 UTCEPSS rescore
  7. 2026-07-24 14:17 UTCEPSS rescore
  8. 2026-07-23 14:18 UTCEPSS rescore
  9. 2026-07-23 14:18 UTCEPSS rescore
  10. 2026-07-23 03:06 UTCEG score recompute
  11. 2026-07-22 14:08 UTCEPSS rescore
  12. 2026-07-21 15:24 UTCEPSS rescore
  13. 2026-07-21 15:24 UTCEPSS rescore
  14. 2026-07-20 17:08 UTCEPSS rescore
  15. 2026-07-19 14:31 UTCEPSS rescore
  16. 2026-07-19 14:31 UTCEPSS rescore
  17. 2026-07-19 02:29 UTCEPSS rescore
  18. 2026-07-19 02:28 UTCEPSS rescore
  19. 2026-07-18 10:04 UTCEPSS rescore
  20. 2026-07-18 10:04 UTCEPSS rescore
  21. 2026-07-17 07:16 UTCOSV refresh
  22. 2026-07-16 17:03 UTCEPSS rescore
  23. 2026-07-16 17:03 UTCEPSS rescore
  24. 2026-07-15 16:57 UTCEPSS rescore
  25. 2026-07-15 16:57 UTCEPSS rescore
Show 75 more
  1. 2026-07-15 02:00 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-14 13:19 UTCNVD updateCVSS v3 → 5.5 · severity → MEDIUM
  4. 2026-07-14 13:11 UTCMITRE cvelistV5
  5. 2026-07-13 22:30 UTCEPSS rescore
  6. 2026-07-13 06:13 UTCEPSS rescore
  7. 2026-07-13 06:13 UTCEPSS rescore
  8. 2026-07-12 05:46 UTCEPSS rescore
  9. 2026-07-12 05:46 UTCEPSS rescore
  10. 2026-07-11 08:27 UTCEPSS rescore
  11. 2026-07-09 19:10 UTCEPSS rescore
  12. 2026-07-08 15:15 UTCEPSS rescore
  13. 2026-07-08 15:15 UTCEPSS rescore
  14. 2026-07-07 13:46 UTCEPSS rescore
  15. 2026-07-06 16:27 UTCEPSS rescore
  16. 2026-07-06 16:27 UTCEPSS rescore
  17. 2026-07-06 02:23 UTCEPSS rescore
  18. 2026-07-06 02:23 UTCEPSS rescore
  19. 2026-07-05 02:30 UTCEPSS rescore
  20. 2026-07-04 06:31 UTCEPSS rescore
  21. 2026-07-04 06:31 UTCEPSS rescore
  22. 2026-07-01 15:06 UTCEPSS rescore
  23. 2026-07-01 15:06 UTCEPSS rescore
  24. 2026-06-30 23:22 UTCEPSS rescore
  25. 2026-06-30 23:22 UTCEPSS rescore
  26. 2026-06-29 14:06 UTCEPSS rescore
  27. 2026-06-29 05:02 UTCOSV refresh
  28. 2026-06-28 14:07 UTCEPSS rescore
  29. 2026-06-28 14:07 UTCEPSS rescore
  30. 2026-06-28 04:56 UTCEPSS rescore
  31. 2026-06-28 04:56 UTCEPSS rescore
  32. 2026-06-27 03:08 UTCEPSS rescore
  33. 2026-06-25 13:49 UTCEPSS rescore
  34. 2026-06-25 13:49 UTCEPSS rescore
  35. 2026-06-24 14:05 UTCEPSS rescore
  36. 2026-06-24 14:05 UTCEPSS rescore
  37. 2026-06-23 21:33 UTCEPSS rescore
  38. 2026-06-23 21:32 UTCEPSS rescore
  39. 2026-06-22 14:25 UTCEPSS rescore
  40. 2026-06-22 14:25 UTCEPSS rescore
  41. 2026-06-21 14:56 UTCEPSS rescore
  42. 2026-06-21 14:56 UTCEPSS rescore
  43. 2026-06-21 01:59 UTCEPSS rescore
  44. 2026-06-21 01:59 UTCEPSS rescore
  45. 2026-06-19 19:25 UTCEPSS rescore
  46. 2026-06-19 19:25 UTCEPSS rescore
  47. 2026-06-18 17:52 UTCEPSS rescore
  48. 2026-06-17 17:53 UTCEPSS rescore
  49. 2026-06-17 17:53 UTCEPSS rescore
  50. 2026-06-16 17:52 UTCEPSS rescore
  51. 2026-06-15 17:48 UTCEPSS rescore
  52. 2026-06-14 23:18 UTCEPSS rescore
  53. 2026-06-13 23:00 UTCEPSS rescore
  54. 2026-06-13 23:00 UTCEPSS rescore
  55. 2026-06-12 23:12 UTCEPSS rescore
  56. 2026-06-11 23:32 UTCVendor advisory
  57. 2026-06-11 23:32 UTCGHSA enrichment
  58. 2026-06-11 14:00 UTCEPSS rescore
  59. 2026-06-10 22:18 UTCEPSS rescore
  60. 2026-06-10 15:01 UTCVendor advisory
  61. 2026-06-10 15:01 UTCGHSA enrichment
  62. 2026-06-10 13:22 UTCEPSS rescore
  63. 2026-06-09 15:58 UTCVendor advisory
  64. 2026-06-09 15:58 UTCGHSA enrichment
  65. 2026-06-08 14:34 UTCVendor advisory
  66. 2026-06-08 14:34 UTCGHSA enrichment
  67. 2026-06-08 14:17 UTCEPSS rescore
  68. 2026-06-08 14:17 UTCEPSS rescore
  69. 2026-06-07 15:25 UTCEPSS rescore
  70. 2026-06-07 15:24 UTCEPSS rescore
  71. 2026-06-07 12:35 UTCEG score recompute▲ 5.50
  72. 2026-06-07 12:35 UTCVendor advisory
  73. 2026-06-07 12:35 UTCGHSA enrichment
  74. 2026-06-06 13:47 UTCEPSS rescore
  75. 2026-06-06 13:47 UTCEPSS rescore

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-23300?
CVE-2026-23300 is a medium vulnerability published on March 25, 2026. In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6nhinit() misclassifies it as a reject…
When was CVE-2026-23300 disclosed?
CVE-2026-23300 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-2026-23300 actively exploited?
CVE-2026-23300 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 97.1% of all scored CVEs.
What is the CVSS score of CVE-2026-23300?
CVE-2026-23300 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-23300?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23300, 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

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