CVE-2026-39903

HIGHPre-NVD 7.17.1
EchelonGraph scoreMEDIUM confidence

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

Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2026-07-10. The CNA's CVSS baseline 7.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: the CNA's CVSS, EPSS, GitHub Security Advisory
7.1EG
EchelonGraph verdictPlan mitigationRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.1Exploit: None knownExposed services: Not assessed

An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.

Simple Machines Forum 2.1 prior to commit 7d048f8 and 3.0 prior to commit a7875e8 contains an authorization bypass vulnerability in Sources/Actions/AttachmentApprove.php where a single-character operator error causes the permission check to always pass regardless of user permissions. An authenticated low-privileged user can approve, reject, or delete any pending attachments on any board without holding the required approve_posts permission, bypass moderation queues for their own uploads, and enumerate and delete other users' pending attachments.

CVSS v3
7.1
EG Score
7.1HIGHmedium confidence
EG Risk
32
EG Risk 32/100

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 (value × EchelonGraph’s weight)
Severity71% × 45%
The EG Score, 7.1 of 10.
Exploitation0.5% × 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: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.
EPSS PROB
0.5%
EPSS %ILE
38th
KEV
Not listed

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

An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.

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.

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

July 10, 2026

Last Modified

July 28, 2026

Advisory Details (5)

Auto-updated Jul 10, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
Web page

Simple Machines Forum Authorization Bypass via AttachmentApprove.php | Advisories | VulnCheck

https://www.vulncheck.com/advisories/simple-machines-forum-authorization-bypass-via-attachmentapprove-php
GitHub pull request

[2.1] Fixes a couple things with attachments and the image proxy

Fix merged in SimpleMachines/SMF PR #9182 on 2026-04-08 — awaiting tagged release

https://github.com/SimpleMachines/SMF/pull/9182
GitHub pull request

[3.0] Fixes a couple things with attachments and the image proxy

Fix merged in SimpleMachines/SMF PR #9181 on 2026-04-08 — awaiting tagged release

https://github.com/SimpleMachines/SMF/pull/9181
GitHub commit

commit a7875e876a64 (SimpleMachines/SMF)

Fix landed in SimpleMachines/SMF commit a7875e876a64 — awaiting tagged release

https://github.com/SimpleMachines/SMF/commit/a7875e876a647572dd4c45da881b875092caac3d
GitHub commit

commit 7d048f8d66aa (SimpleMachines/SMF)

Fix landed in SimpleMachines/SMF commit 7d048f8d66aa — awaiting tagged release

https://github.com/SimpleMachines/SMF/commit/7d048f8d66aab9af51cd6ee110fbad103cf673e8

Vendor Advisories for CVE-2026-39903(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 37× 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 223 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 124 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  3. 2026-10-12 16:10 UTCEG score recompute
  4. 2026-10-11 19:52 UTCEG score recompute
  5. 2026-10-11 17:05 UTCEG score recompute
  6. 2026-10-11 14:32 UTCEG score recompute
  7. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  10. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  12. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  13. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  14. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  15. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  16. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  17. 2026-10-01 15:11 UTCEG score recompute
  18. 2026-10-01 15:11 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  19. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  20. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  21. 2026-09-28 09:48 UTCEG score recompute
  22. 2026-09-28 09:48 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  24. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  25. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.5% · 37th percentile
Show 74 more
  1. 2026-09-24 11:13 UTCEG score recompute
  2. 2026-09-24 11:13 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  3. 2026-09-23 05:45 UTCEG score recompute
  4. 2026-09-23 05:45 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  5. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  6. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  7. 2026-09-18 05:19 UTCEG score recompute
  8. 2026-09-18 05:19 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  9. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  10. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  11. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  12. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  13. 2026-09-13 23:40 UTCEG score recompute
  14. 2026-09-13 23:40 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  15. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  16. 2026-09-13 08:12 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  17. 2026-09-12 16:06 UTCEG score recompute
  18. 2026-09-12 16:06 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  19. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  20. 2026-09-12 02:57 UTCEG score recompute
  21. 2026-09-12 02:57 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  22. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  23. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  24. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  25. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  26. 2026-09-08 02:54 UTCEG score recompute
  27. 2026-09-08 02:54 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  28. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  29. 2026-09-06 13:57 UTCEG score recompute
  30. 2026-09-06 13:57 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  31. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  32. 2026-09-05 21:45 UTCEG score recompute
  33. 2026-09-05 21:44 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  34. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  35. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  36. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  37. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  38. 2026-08-30 19:34 UTCEG score recompute
  39. 2026-08-30 19:34 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  40. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  41. 2026-08-30 06:25 UTCEG score recompute
  42. 2026-08-30 06:25 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  43. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  44. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  45. 2026-08-27 21:41 UTCEG score recompute
  46. 2026-08-27 21:41 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  47. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  48. 2026-08-27 00:48 UTCEG score recompute
  49. 2026-08-27 00:48 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  50. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  51. 2026-08-26 03:39 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  52. 2026-08-25 13:56 UTCEG score recompute
  53. 2026-08-25 13:56 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  54. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  55. 2026-08-25 00:41 UTCEG score recompute
  56. 2026-08-25 00:41 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  57. 2026-08-24 11:29 UTCEG score recompute
  58. 2026-08-24 11:29 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  59. 2026-08-23 22:18 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  60. 2026-08-23 08:58 UTCEG score recompute
  61. 2026-08-23 08:58 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  62. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  63. 2026-08-22 19:50 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  64. 2026-08-22 06:41 UTCEG score recompute
  65. 2026-08-22 06:41 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  66. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  67. 2026-08-21 17:32 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  68. 2026-08-21 04:22 UTCEG score recompute
  69. 2026-08-21 04:22 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  70. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  71. 2026-08-20 15:12 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  72. 2026-08-20 01:32 UTCEG score recompute
  73. 2026-08-20 01:32 UTCGHSA enrichmentGHSA-62g6-4j9c-6v7p · GitHub severity HIGH · GitHub CVSS 7.1
  74. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.3% · 26th percentile

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-39903?
CVE-2026-39903 is a high-severity vulnerability; its CVE record was published on July 10, 2026. Simple Machines Forum 2.1 prior to commit 7d048f8 and 3.0 prior to commit a7875e8 contains an authorization bypass vulnerability in Sources/Actions/AttachmentApprove.php where a single-character operator error causes the permission check to always pass regardless of user permissions. An…
When was CVE-2026-39903 made public?
CVE-2026-39903 was made public on April 7, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on July 10, 2026. EchelonGraph's copy of the record carries a last-modified date of July 28, 2026; the record at its source may have been updated since.
Is CVE-2026-39903 actively exploited?
CVE-2026-39903 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (38th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-39903?
CVE-2026-39903 has a CVSS base score of 7.1 (the CNA's own assessment, by vulncheck; NVD's own analysis pending).
How do I remediate CVE-2026-39903?
An upstream fix for CVE-2026-39903 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-39903 are linked in the Vendor Advisories panel on this page.

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