CVE-2026-45125

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreMEDIUM confidence

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

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (33rd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
5.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

MyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=do_emailuser accepts the fromname HTTP parameter for guests or the stored username for authenticated users when the cansendemail group permission is enabled. When mail_handler is set to the default PHP mail value, the sender name is used without sanitization in Return-Path and Reply-To headers, allowing arbitrary headers to be injected with CRLF sequences. This issue is fixed in version 1.8.40.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
39
EG Risk 39/100

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)
Severity53% × 45%
The EG Score, 5.3 of 10.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (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 at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
33rd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (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)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (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

August 18, 2026

Last Modified

September 8, 2026

Advisory Details (4)

Auto-updated Aug 18, 2026
Patch available. Sources: github, github_commit, github_release.
Web page

Version 1.8.40 - MyBB

https://mybb.com/versions/1.8.40
GitHub release Patch Available

mybb_1840

Patch available: mybb/mybb mybb_1840

https://github.com/mybb/mybb/releases/tag/mybb_1840
GitHub commit Patch Available

commit 5046c56b515d (mybb/mybb)

Patch available: mybb/mybb mybb_1840 (contains commit 5046c56b515d)

https://github.com/mybb/mybb/commit/5046c56b515d4593297a4f65b0c6ccb0b55baa01
GitHub advisoryMentions a patch (unverified)

Email User CRLF injection · Advisory · mybb/mybb · GitHub

https://github.com/mybb/mybb/security/advisories/GHSA-f626-53q9-pqm9

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 45× 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.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  3. 2026-10-12 16:04 UTCEG score recompute
  4. 2026-10-11 19:46 UTCEG score recompute
  5. 2026-10-11 17:01 UTCEG score recompute
  6. 2026-10-11 14:26 UTCEG score recompute
  7. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  10. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  12. 2026-10-07 11:13 UTCEG score recompute
  13. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  14. 2026-10-06 12:53 UTCEG score recompute
  15. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  16. 2026-10-05 14:22 UTCEG score recompute
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  18. 2026-10-03 17:39 UTCEG score recompute
  19. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  20. 2026-10-02 06:53 UTCEG score recompute
  21. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  22. 2026-10-01 07:53 UTCEG score recompute
  23. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  24. 2026-09-30 09:49 UTCEG score recompute
  25. 2026-09-29 04:04 UTCEG score recompute
Show 68 more
  1. 2026-09-28 05:58 UTCEG score recompute
  2. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  3. 2026-09-27 07:57 UTCEG score recompute
  4. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  5. 2026-09-25 01:29 UTCEG score recompute
  6. 2026-09-23 20:20 UTCEG score recompute
  7. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  8. 2026-09-22 20:26 UTCEG score recompute
  9. 2026-09-21 18:23 UTCEG score recompute
  10. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  11. 2026-09-19 21:54 UTCEG score recompute
  12. 2026-09-18 23:49 UTCEG score recompute
  13. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  14. 2026-09-18 01:47 UTCEG score recompute
  15. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  16. 2026-09-17 03:45 UTCEG score recompute
  17. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  18. 2026-09-16 05:43 UTCEG score recompute
  19. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  20. 2026-09-15 07:40 UTCEG score recompute
  21. 2026-09-14 09:38 UTCEG score recompute
  22. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  23. 2026-09-13 11:36 UTCEG score recompute
  24. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  25. 2026-09-11 15:32 UTCEG score recompute
  26. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  27. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  28. 2026-09-10 17:25 UTCEG score recompute
  29. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  30. 2026-09-09 19:20 UTCEG score recompute
  31. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  32. 2026-09-07 16:08 UTCEG score recompute
  33. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  34. 2026-09-06 14:08 UTCEG score recompute
  35. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  36. 2026-09-05 16:06 UTCEG score recompute
  37. 2026-09-04 18:03 UTCEG score recompute
  38. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  39. 2026-09-02 21:57 UTCEG score recompute
  40. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  41. 2026-09-01 20:11 UTCEG score recompute
  42. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  43. 2026-08-30 23:57 UTCEG score recompute
  44. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  45. 2026-08-30 01:55 UTCEG score recompute
  46. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  47. 2026-08-29 03:53 UTCEG score recompute
  48. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  49. 2026-08-27 22:48 UTCEG score recompute
  50. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  51. 2026-08-27 00:46 UTCEG score recompute
  52. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  53. 2026-08-26 02:44 UTCEG score recompute
  54. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  55. 2026-08-25 04:41 UTCEG score recompute
  56. 2026-08-23 08:37 UTCEG score recompute
  57. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  58. 2026-08-22 10:35 UTCEG score recompute
  59. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  60. 2026-08-21 12:33 UTCEG score recompute
  61. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  62. 2026-08-20 14:29 UTCEG score recompute
  63. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  64. 2026-08-18 18:24 UTCEG score recompute
  65. 2026-08-18 18:00 UTCEG score recompute
  66. 2026-08-18 16:28 UTCEG score recompute
  67. 2026-08-18 15:59 UTCEG score recomputeFirst assessed: 5.3 MEDIUM
  68. 2026-08-18 15:59 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-45125?
CVE-2026-45125 is a medium-severity vulnerability; its CVE record was published on August 18, 2026. MyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=doemailuser accepts the fromname HTTP parameter for guests or the stored username for authenticated users when the…
When was the CVE record for CVE-2026-45125 published?
The CVE record for CVE-2026-45125 was published on August 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 September 8, 2026; the record at its source may have been updated since.
Is CVE-2026-45125 actively exploited?
CVE-2026-45125 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (33rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-45125?
CVE-2026-45125 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-45125?
A fix for CVE-2026-45125 is available: update to the fixed version the vendor names in its advisory.

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