CVE-2026-23990

MEDIUMNVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

Score 5.3 from GitHub Security Advisory (severity: MODERATE) published 2026-01-21. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-4140 (ENISA EUVD) · GHSA-4xh5-jcj2-ch8q (GitHub Security Advisories) · GO-2026-4351 (OSV.dev)Source: ENISA EUVD

5.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

The Flux Operator is a Kubernetes CRD controller that manages the lifecycle of CNCF Flux CD and the ControlPlane enterprise distribution. Starting in version 0.36.0 and prior to version 0.40.0, a privilege escalation vulnerability exists in the Flux Operator Web UI authentication code that allows an attacker to bypass Kubernetes RBAC impersonation and execute API requests with the operator's service account privileges. In order to be vulnerable, cluster admins must configure the Flux Operator with an OIDC provider that issues tokens lacking the expected claims (e.g., email, groups), or configure custom CEL expressions that can evaluate to empty values. After OIDC token claims are processed through CEL expressions, there is no validation that the resulting username and groups values are non-empty. When both values are empty, the Kubernetes client-go library does not add impersonation headers to API requests, causing them to be executed with the flux-operator service account's credentials instead of the authenticated user's limited permissions. This can result in privilege escalation, data exposure, and/or information disclosure. Version 0.40.0 patches the issue.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
24
EG Risk 24/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity53% × 45%
Impact severity (EG Severity): CVSS 5.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
28th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.

EG Severity
5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

January 21, 2026

Last Modified

June 17, 2026

Advisory Details (4)

Auto-updated Aug 9, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
GitHub advisoryMentions a patch (unverified)

Web UI Impersonation Bypass via Empty OIDC Claims · Advisory · controlplaneio-fluxcd/flux-operator · GitHub

https://github.com/controlplaneio-fluxcd/flux-operator/security/advisories/GHSA-4xh5-jcj2-ch8q
GitHub release Patch Available

v0.40.0

Patch available: controlplaneio-fluxcd/flux-operator v0.40.0

https://github.com/controlplaneio-fluxcd/flux-operator/releases/tag/v0.40.0
GitHub pull request

web: strict validation for RBAC impersonation

Fix merged in controlplaneio-fluxcd/flux-operator PR #610 on 2026-01-20 — awaiting tagged release

https://github.com/controlplaneio-fluxcd/flux-operator/pull/610
GitHub commit

commit 084540424f6d (controlplaneio-fluxcd/flux-operator)

Fix landed in controlplaneio-fluxcd/flux-operator commit 084540424f6d — awaiting tagged release

https://github.com/controlplaneio-fluxcd/flux-operator/commit/084540424f6de8ba5d88fb1fd1e8472ba29afd7e

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
gogithub.com/controlplaneio-fluxcd/flux-operator @ 0.40.0 (fixes >= 0.36.0, < 0.40.0)—ghsa

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.

Affected Packages

(1 across 1 ecosystem)
Go(1)
PackageVulnerable rangeFix by version rangeDependents
github.com/controlplaneio-fluxcd/flux-operator—
  • 0.36.0 up to 0.40.0: fixed in 0.40.0
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 41× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 209 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 110 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  3. 2026-11-01 07:57 UTCGHSA enrichmentGHSA-4xh5-jcj2-ch8q · GitHub severity MODERATE · GitHub CVSS 5.3
  4. 2026-11-01 07:57 UTCEG score recompute
  5. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  6. 2026-10-31 02:55 UTCOSV refresh
  7. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  8. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  9. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  10. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  12. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.3% · 28th percentile
  13. 2026-10-25 14:41 UTCEG score recompute
  14. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  15. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  16. 2026-10-23 04:57 UTCEG score recompute
  17. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  18. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  19. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  20. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  21. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  22. 2026-10-18 03:54 UTCEG score recompute
  23. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  24. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  25. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.4% · 27th percentile
Show 74 more
  1. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  2. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  3. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  4. 2026-10-12 16:20 UTCEG score recompute
  5. 2026-10-11 20:02 UTCEG score recompute
  6. 2026-10-11 17:15 UTCEG score recompute
  7. 2026-10-11 14:47 UTCEG score recompute
  8. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  11. 2026-10-08 19:56 UTCOSV refresh
  12. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  13. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  14. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  15. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  16. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  17. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  18. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  19. 2026-09-29 15:21 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  20. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  21. 2026-09-27 13:47 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  22. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  23. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  24. 2026-09-24 14:03 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  25. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  26. 2026-09-19 02:00 UTCOSV refresh
  27. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  28. 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  29. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  30. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  31. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  32. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  33. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  34. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  35. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  36. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  37. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  38. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  39. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  40. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  41. 2026-08-31 05:49 UTCOSV refresh
  42. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  43. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  44. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  45. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  46. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  47. 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  48. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  49. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  50. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  51. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  52. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  53. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  54. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  55. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  56. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  57. 2026-08-14 13:12 UTCEG score recompute
  58. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  59. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  60. 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  61. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  62. 2026-08-09 18:57 UTCEG score recompute
  63. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  64. 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  65. 2026-08-08 00:03 UTCEG score recompute
  66. 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  67. 2026-08-06 05:19 UTCEG score recompute
  68. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  69. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  70. 2026-08-04 10:38 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  71. 2026-08-03 10:35 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  72. 2026-08-02 22:38 UTCEG score recompute
  73. 2026-08-02 02:26 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  74. 2026-08-01 04:15 UTCEPSS rescoreEPSS 0.3% · 22nd percentile

Frequently asked(5)

What is CVE-2026-23990?
CVE-2026-23990 is a medium-severity vulnerability; its CVE record was published on January 21, 2026. The Flux Operator is a Kubernetes CRD controller that manages the lifecycle of CNCF Flux CD and the ControlPlane enterprise distribution. Starting in version 0.36.0 and prior to version 0.40.0, a privilege escalation vulnerability exists in the Flux Operator Web UI authentication code that allows…
When was the CVE record for CVE-2026-23990 published?
The CVE record for CVE-2026-23990 was published on January 21, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of June 17, 2026; the record at its source may have been updated since.
Is CVE-2026-23990 actively exploited?
CVE-2026-23990 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (28th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-23990?
CVE-2026-23990 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-23990?
A fix for CVE-2026-23990 is available: update to the fixed version the vendor names in its advisory.

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