CVE-2026-40487

CRITICALNVD 9.09.0
EchelonGraph scoreMEDIUM confidence

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

This critical-severity CVE scores 9.0 under NVD CVSS v3. EPSS exploit probability: 0.2% (13th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Elevated

Also known asEUVD-2026-23634 (ENISA EUVD)Source: ENISA EUVD

9.0EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 9.0Exploit: Public PoCExposed services: Not assessed

The CVE record names the fixed release — apply it.

Postiz is an AI social media scheduling tool. Prior to version 2.21.6, a file upload validation bypass allows any authenticated user to upload arbitrary HTML, SVG, or other executable file types to the server by spoofing the Content-Type header. The uploaded files are then served by nginx with a Content-Type derived from their original extension (text/html, image/svg+xml), enabling Stored Cross-Site Scripting (XSS) in the context of the application's origin. This can lead to session riding, account takeover, and full compromise of other users' accounts. Version 2.21.6 contains a fix.

CVSS v3
9.0
EG Score
9.0CRITICALmedium confidence
EG Risk
57
EG Risk 57/100

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)
Severity90% × 45%
Impact severity (EG Severity): CVSS 9.0 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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: The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.2%
EPSS %ILE
13th
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 (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is its impact severity (EG Severity), not escalated.

EG Severity
9.0 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). 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 low, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 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 low, Track* at medium and Attend at high mission impact.

The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 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 total (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

April 18, 2026

Last Modified

October 26, 2026

Advisory Details (2)

Auto-updated May 2, 2026
Fix named in the CVE record. Sources: github.
GitHub advisoryMentions a patch (unverified)

Unrestricted File Upload via MIME Type Spoofing Leads to Stored XSS · Advisory · gitroomhq/postiz-app · GitHub

https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-44wg-r34q-hvfx
Web page

Release v2.21.6 · gitroomhq/postiz-app · GitHub

https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.6

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 32× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 237 rows on record for this CVE, as 99 entries (1 repeat merged).

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 137 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 02:39 UTCEchelonGraph re-scored
  2. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  3. 2026-11-12 04:56 UTCEchelonGraph re-scored
  4. 2026-11-11 16:39 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  5. 2026-11-11 07:13 UTCEchelonGraph re-scored
  6. 2026-11-10 16:43 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  7. 2026-11-10 09:25 UTCEchelonGraph re-scored
  8. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  9. 2026-11-09 11:42 UTCEchelonGraph re-scored
  10. 2026-11-08 16:39 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  11. 2026-11-08 13:59 UTCEchelonGraph re-scored
  12. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  13. 2026-11-06 18:30 UTCEchelonGraph re-scored
  14. 2026-11-06 16:37 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  15. 2026-11-06 07:55 UTCOSV refresh
  16. 2026-11-05 20:46 UTCEchelonGraph re-scored
  17. 2026-11-05 16:37 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  18. 2026-11-04 23:03 UTCEchelonGraph re-scored
  19. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  20. 2026-11-04 01:20 UTCEchelonGraph re-scored
  21. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  22. 2026-11-03 03:33 UTCEchelonGraph re-scored
  23. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  24. 2026-11-02 05:50 UTCEchelonGraph re-scored
  25. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
Show 74 more
  1. 2026-11-01 08:06 UTCEchelonGraph re-scored
  2. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  3. 2026-10-31 10:21 UTCEchelonGraph re-scored
  4. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  5. 2026-10-30 12:35 UTCEchelonGraph re-scored
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  7. 2026-10-28 17:06 UTCEchelonGraph re-scored
  8. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  9. 2026-10-27 19:23 UTCEchelonGraph re-scored
  10. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  11. 2026-10-26 21:40 UTCEchelonGraph re-scored▲ 0.10
  12. 2026-10-26 21:26 UTCNVD updateCVSS v3 → 9 · severity → CRITICAL
  13. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  14. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  15. 2026-10-25 14:31 UTCEchelonGraph re-scored
  16. 2026-10-25 03:06 UTCEchelonGraph re-scored
  17. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  18. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  19. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  20. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  21. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  22. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  23. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  24. 2026-10-18 03:42 UTCEchelonGraph re-scored
  25. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  26. 2026-10-17 14:50 UTCEchelonGraph re-scored
  27. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  28. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  29. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  30. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  31. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  32. 2026-10-12 16:09 UTCEchelonGraph re-scored
  33. 2026-10-11 19:51 UTCEchelonGraph re-scored
  34. 2026-10-11 17:05 UTCEchelonGraph re-scored
  35. 2026-10-11 14:31 UTCEchelonGraph re-scored
  36. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  37. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  38. 2026-10-10 18:55 UTCOSV refresh
  39. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  40. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  41. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  42. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  43. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  44. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  45. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  46. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  47. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  48. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  49. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  50. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  51. 2026-09-21 06:19 UTCOSV refresh
  52. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  53. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  54. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  55. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  56. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  57. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  58. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  59. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  60. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  61. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  62. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  63. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  64. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  65. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  66. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  67. 2026-09-02 03:40 UTCOSV refresh
  68. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  69. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  70. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  71. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  72. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  73. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  74. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 12th percentile

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 GitHub PoC). Defenders should treat patch urgency accordingly.

  • GitHub PoCAstaruf/CVE-2026-40487
    Published Apr 15, 2026

    CVE-2026-40487 - Postiz <= 2.21.5 - Arbitrary File Upload via MIME-Type Spoofing → Stored XSS → Account Takeover

    Open source ↗

Frequently asked(5)

What is CVE-2026-40487?
CVE-2026-40487 is a critical-severity vulnerability; its CVE record was published on April 18, 2026. Postiz is an AI social media scheduling tool. Prior to version 2.21.6, a file upload validation bypass allows any authenticated user to upload arbitrary HTML, SVG, or other executable file types to the server by spoofing the Content-Type header. The uploaded files are then served by nginx with a…
When was the CVE record for CVE-2026-40487 published?
The CVE record for CVE-2026-40487 was published on April 18, 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 October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-40487 actively exploited?
CVE-2026-40487 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (13th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-40487?
CVE-2026-40487 has a CVSS v3 base score of 9.0 (NVD).
How do I remediate CVE-2026-40487?
The CVE record for CVE-2026-40487 names the fix: "Version 2.21.6 contains a fix."

Dependency Blast Radius

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