CVE-2026-76847

HIGHPre-NVD 8.88.8
EchelonGraph scoreMEDIUM confidence

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

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-08-24. A secondary CVSS source baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 3 sources updated this week
8.8EG
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: 0.4%CVSS: 8.8Exploit: None knownExposed services: Not assessed

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

The CVE record's CNA (VulnCheck) lists nektos act versions 0.2.81 up to and including 0.2.89 as affected. No release containing a fix is confirmed on record.

act starts an HTTP Artifacts V4 backend whenever a workflow uses actions/upload-artifact@v4 or actions/download-artifact@v4. The control-plane RPCs of that backend, including CreateArtifact, GetSignedArtifactURL, ListArtifacts, FinalizeArtifact and DeleteArtifact, accept a caller-supplied workflow_run_backend_id and never check that it belongs to the requester: validateRunIDV4 in pkg/artifacts/artifacts_v4.go parses the value and returns it with the comparison against the requesting task's run ID left commented out. The signed URLs the backend issues are authenticated by an HMAC whose key is hardcoded to the four bytes 0xba 0xdb 0xee 0xf0, identical in every build, computed over a concatenation of endpoint, expiry, artifact name and task ID with no length prefix or delimiter, so signatures are both forgeable and ambiguous between differing artifact name and task ID pairs. The --artifact-server-addr flag defaults to the host's outbound address rather than loopback, leaving the backend reachable from the surrounding network. Any client that can reach it may read, overwrite or delete the artifacts of a concurrently running job with no credentials, exposing build outputs such as secrets and deployment credentials and permitting their replacement before the owning job consumes them.

CVSS v3
8.8
EG Score
8.8HIGHmedium confidence
EG Risk
40
EG Risk 40/100

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)
Severity88% × 45%
The EG Score, 8.8 of 10.
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 low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (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: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.4%
EPSS %ILE
26th
KEV
Not listed

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

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation none (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.

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

August 24, 2026

Last Modified

October 12, 2026

Advisory Details (4)

Auto-updated Aug 24, 2026
No fix on record yet.
Web page

act 0.2.81 through 0.2.89 Missing Authorization in the Artifacts V4 Backend | Advisories | VulnCheck

https://www.vulncheck.com/advisories/act-through-missing-authorization-in-the-artifacts-v4-backend
Web page

act/cmd/root.go at v0.2.89 · nektos/act · GitHub

https://github.com/nektos/act/blob/v0.2.89/cmd/root.go
Web page

act/pkg/artifacts/artifacts_v4.go at v0.2.89 · nektos/act · GitHub

https://github.com/nektos/act/blob/v0.2.89/pkg/artifacts/artifacts_v4.go
Web page

GitHub - nektos/act: Run your GitHub Actions locally 🚀 · GitHub

https://github.com/nektos/act

Vendor Advisories for CVE-2026-76847(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 18× in last 7d / 97× 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 176 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 76 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  2. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  3. 2026-10-12 15:26 UTCEG score recompute
  4. 2026-10-12 15:26 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  5. 2026-10-11 19:23 UTCEG score recompute
  6. 2026-10-11 16:39 UTCEG score recompute
  7. 2026-10-11 13:58 UTCEG score recompute
  8. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  10. 2026-10-10 13:00 UTCEG score recompute
  11. 2026-10-10 13:00 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  13. 2026-10-09 04:54 UTCEG score recompute
  14. 2026-10-09 04:54 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  15. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  16. 2026-10-08 04:02 UTCEG score recompute
  17. 2026-10-08 04:02 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  18. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  19. 2026-10-07 05:36 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  20. 2026-10-06 16:40 UTCEG score recompute
  21. 2026-10-06 16:40 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  22. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  23. 2026-10-06 02:53 UTCEG score recompute
  24. 2026-10-06 02:53 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  25. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 26th percentile
Show 75 more
  1. 2026-10-05 09:37 UTCEG score recompute
  2. 2026-10-05 09:37 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  3. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  4. 2026-10-04 20:43 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  5. 2026-10-04 05:27 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  6. 2026-10-03 16:33 UTCEG score recompute
  7. 2026-10-03 16:33 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  8. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  9. 2026-10-03 01:49 UTCEG score recompute
  10. 2026-10-03 01:49 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  11. 2026-10-02 12:54 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  12. 2026-10-01 22:43 UTCEG score recompute
  13. 2026-10-01 22:43 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  14. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  15. 2026-10-01 09:14 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  16. 2026-09-30 20:19 UTCEG score recompute
  17. 2026-09-30 20:19 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  18. 2026-09-30 07:15 UTCEG score recompute
  19. 2026-09-30 07:15 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  20. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  21. 2026-09-29 05:21 UTCEG score recompute
  22. 2026-09-29 05:21 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  23. 2026-09-28 16:27 UTCEG score recompute
  24. 2026-09-28 16:27 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  25. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  26. 2026-09-28 03:28 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  27. 2026-09-27 14:33 UTCEG score recompute
  28. 2026-09-27 14:33 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  29. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  30. 2026-09-27 00:41 UTCEG score recompute
  31. 2026-09-27 00:41 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  32. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  33. 2026-09-26 00:28 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  34. 2026-09-25 10:15 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  35. 2026-09-24 21:20 UTCEG score recompute
  36. 2026-09-24 21:20 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  37. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.4% · 25th percentile
  38. 2026-09-24 10:16 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  39. 2026-09-23 21:21 UTCEG score recompute
  40. 2026-09-23 21:21 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  41. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  42. 2026-09-23 08:26 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  43. 2026-09-22 19:31 UTCEG score recompute
  44. 2026-09-22 19:31 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  45. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  46. 2026-09-22 04:35 UTCEG score recompute
  47. 2026-09-22 04:35 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  48. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  49. 2026-09-21 15:38 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  50. 2026-09-21 02:43 UTCEG score recompute
  51. 2026-09-21 02:43 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  52. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  53. 2026-09-20 13:48 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  54. 2026-09-20 00:52 UTCEG score recompute
  55. 2026-09-20 00:52 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  56. 2026-09-19 11:57 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  57. 2026-09-18 23:02 UTCEG score recompute
  58. 2026-09-18 23:02 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  59. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  60. 2026-09-18 10:07 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  61. 2026-09-17 21:12 UTCEG score recompute
  62. 2026-09-17 21:12 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  63. 2026-09-17 03:35 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  64. 2026-09-16 14:40 UTCEG score recompute
  65. 2026-09-16 14:40 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  66. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  67. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  68. 2026-09-16 01:41 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  69. 2026-09-15 12:46 UTCEG score recompute
  70. 2026-09-15 12:46 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  71. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  72. 2026-09-14 23:51 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  73. 2026-09-14 10:56 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8
  74. 2026-09-13 22:01 UTCEG score recompute
  75. 2026-09-13 22:01 UTCGHSA enrichmentGHSA-crfw-6q9f-w49f · GitHub severity HIGH · GitHub CVSS 8.8

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-76847?
CVE-2026-76847 is a high-severity vulnerability; its CVE record was published on August 24, 2026. act starts an HTTP Artifacts V4 backend whenever a workflow uses actions/upload-artifact@v4 or actions/download-artifact@v4. The control-plane RPCs of that backend, including CreateArtifact, GetSignedArtifactURL, ListArtifacts, FinalizeArtifact and DeleteArtifact, accept a caller-supplied…
When was CVE-2026-76847 made public?
CVE-2026-76847 was made public on August 18, 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 August 24, 2026. EchelonGraph's copy of the record carries a last-modified date of October 12, 2026; the record at its source may have been updated since.
Is CVE-2026-76847 actively exploited?
CVE-2026-76847 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (26th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-76847?
CVE-2026-76847 has a CVSS base score of 8.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-76847?
No fix for CVE-2026-76847 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 CVE record's CNA (VulnCheck) lists nektos act versions 0.2.81 up to and including 0.2.89 as affected. No release containing a fix is confirmed on record. The vendor advisories EchelonGraph has for CVE-2026-76847 are linked in the Vendor Advisories panel on this page.

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