CVE-2026-77999

HIGHPre-NVD 8.78.7
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (37th 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
Trending — 3 sources updated this week

Also known asEUVD-2026-70415 (ENISA EUVD) · GHSA-ffqf-m6vh-866w (GitHub Security Advisories)Source: ENISA EUVD

8.7EG
EchelonGraph verdictPlan mitigationNo fix is confirmed yet: check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 8.7Exploit: None knownExposed services: Not assessed

No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.

Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (_validateIPN()) accepted UNVERIFIED and any non-INVALID response as valid, made its verification request with CURLOPT_SSL_VERIFYPEER disabled, and stored its verdict in a field nothing downstream ever checked — so processing continued regardless of the outcome. Separately, the paid-amount comparison only ran when mc_gross was a positive number; omitting the field from the POST body (floatval(null) == 0) skipped the check entirely. Combined with a merchant-configured receiver_email and a sequential, enumerable order id read from the custom field, an anonymous POST was enough to move a pending order straight to CONFIRMED with no payment, or force another customer's pending order to FAILED. paypalv2.php performed no amount check under any circumstances.

CVSS v3
8.7
EG Score
8.7HIGHmedium confidence
EG Risk
54
EG Risk 54/100

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)
Severity87% × 45%
Impact severity (EG Severity): CVSS 8.7 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.
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: No fix is confirmed yet. Check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
37th
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 (8.7): severity, escalated by confirmed exploitation. This CVE's 8.7 is its impact severity (EG Severity), not escalated.

EG Severity
8.7 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-27). 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 or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.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 or medium mission impact; Attend at high (mission-essential systems).

No fix is confirmed yet. Check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule 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.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.

The score's inputs: 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

September 3, 2026

Last Modified

September 3, 2026

Advisory Details (1)

Auto-updated Sep 3, 2026
No fix on record yet.
Web page

Powerful and intuitive Joomla eCommerce. - J2Commerce

https://www.j2commerce.com/

Vendor Advisories for CVE-2026-77999(1)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 60× 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 100 of 172 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. None are among the latest 100 rows. The 72 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  3. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  4. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  5. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  6. 2026-10-28 16:00 UTCEG score recompute
  7. 2026-10-28 16:00 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  9. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  10. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  11. 2026-10-25 14:01 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  14. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  15. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  16. 2026-10-20 19:49 UTCEG score recompute
  17. 2026-10-20 19:49 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  18. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  19. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  20. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  21. 2026-10-18 03:11 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  23. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
Show 75 more
  1. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  2. 2026-10-13 06:53 UTCEG score recompute
  3. 2026-10-13 06:52 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  4. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  5. 2026-10-12 15:37 UTCEG score recompute
  6. 2026-10-11 19:23 UTCEG score recompute
  7. 2026-10-11 16:39 UTCEG score recompute
  8. 2026-10-11 13:57 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  11. 2026-10-10 11:45 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  12. 2026-10-09 23:42 UTCEG score recompute
  13. 2026-10-09 23:41 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  14. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  15. 2026-10-09 01:34 UTCEG score recompute
  16. 2026-10-09 01:34 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  17. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  18. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  19. 2026-10-07 23:35 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  20. 2026-10-07 02:10 UTCEG score recompute
  21. 2026-10-07 02:10 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  22. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  23. 2026-10-06 13:39 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  24. 2026-10-06 01:37 UTCEG score recompute
  25. 2026-10-06 01:37 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  26. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  27. 2026-10-05 13:27 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  28. 2026-10-05 01:20 UTCEG score recompute
  29. 2026-10-05 01:20 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  30. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  31. 2026-10-04 13:18 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  32. 2026-10-04 01:09 UTCEG score recompute
  33. 2026-10-04 01:09 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  34. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  35. 2026-10-03 12:49 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  36. 2026-10-02 19:53 UTCEG score recompute
  37. 2026-10-02 19:53 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  38. 2026-10-02 07:51 UTCEG score recompute
  39. 2026-10-02 07:51 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  40. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  41. 2026-10-01 19:38 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  42. 2026-10-01 07:18 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  43. 2026-09-30 19:16 UTCEG score recompute
  44. 2026-09-30 19:16 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  45. 2026-09-30 02:58 UTCEG score recompute
  46. 2026-09-30 02:58 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  47. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  48. 2026-09-29 08:50 UTCEG score recompute
  49. 2026-09-29 08:50 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  50. 2026-09-28 20:48 UTCEG score recompute
  51. 2026-09-28 20:48 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  52. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  53. 2026-09-28 05:40 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  54. 2026-09-27 17:38 UTCEG score recompute
  55. 2026-09-27 17:38 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  56. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  57. 2026-09-27 05:35 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  58. 2026-09-26 17:23 UTCEG score recompute
  59. 2026-09-26 17:23 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  60. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  61. 2026-09-26 04:25 UTCEG score recompute
  62. 2026-09-26 04:24 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  63. 2026-09-26 00:28 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  64. 2026-09-25 13:01 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  65. 2026-09-25 00:59 UTCEG score recompute
  66. 2026-09-25 00:59 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  67. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  68. 2026-09-24 12:57 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  69. 2026-09-24 00:53 UTCEG score recompute
  70. 2026-09-24 00:53 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  71. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  72. 2026-09-23 12:51 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  73. 2026-09-23 00:49 UTCEG score recompute
  74. 2026-09-23 00:49 UTCGHSA enrichmentGHSA-ffqf-m6vh-866w · GitHub severity HIGH
  75. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.3% · 17th percentile

Frequently asked(5)

What is CVE-2026-77999?
CVE-2026-77999 is a high-severity vulnerability; its CVE record was published on September 3, 2026. Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (_validateIPN()) accepted UNVERIFIED and any non-INVALID response as valid, made its…
When was the CVE record for CVE-2026-77999 published?
The CVE record for CVE-2026-77999 was published on September 3, 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 3, 2026; the record at its source may have been updated since.
Is CVE-2026-77999 actively exploited?
CVE-2026-77999 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-77999?
CVE-2026-77999 has a CVSS base score of 8.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-77999?
No fix for CVE-2026-77999 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-77999 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-77999

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