CVE-2026-56865

HIGHPre-NVD 8.48.4—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.4 under CISA-ADP (Vulnrichment) CVSS v3.1 (NVD's own analysis pending). EPSS exploit probability: 0.1% (2nd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: cisa-adp, epss
Trending — 3 sources updated this week
8.4EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 8.4Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that cannot be detected by evaluating the transparency log. All tiles are now correctly verified against their parents. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy

CVSS v3
8.4
EG Score
8.4HIGHmedium confidence
EG Risk
38
EG Risk 38/100CISA SSVC

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
Severity84% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.1%
EPSS %ILE
2nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 13, 2026

Last Modified

September 3, 2026

Advisory Details (5)

Auto-updated Aug 14, 2026
Patch available.
generic

GO-2026-6179 - Go Packages

https://pkg.go.dev/vuln/GO-2026-6179
generic
https://go.dev/cl/815020
generic
https://go.dev/cl/814960
generic
https://groups.google.com/g/golang-announce/c/94pEornpRlI
generic

x/mod/sumdb/tlog: fix transparency log tile verification bypass · Issue #80744 · golang/go · GitHub

https://go.dev/issue/80744

Vendor Advisories for CVE-2026-56865(3)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatcluster-observability-operator/cluster-observability-rhel9-operator:17908545992026-10-01redhat
redhatadvanced-cluster-security/rhacs-rhel9-operator:17894113202026-09-15redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(7 across 4 ecosystems)
Debian:14(3)
PackageVulnerable rangeFix by version rangeDependents
golang-1.251.25.0-1 ... 1.25.9-1 (20 versions)
  • every version on: no fix on record
—
golang-1.261.26.0-1 ... 1.26~rc3-2 (16 versions)
  • every version up to 1.26.6-1: fixed in 1.26.6-1
—
golang-1.271.27~rc1-1, 1.27~rc2-1
  • every version up to 1.27~rc3-1: fixed in 1.27~rc3-1
—
Go(2)
PackageVulnerable rangeFix by version rangeDependents
golang.org/x/mod—
  • every version up to 0.40.0: fixed in 0.40.0
—
toolchain—
  • every version up to 1.25.13: fixed in 1.25.13
  • 1.26.0-0 up to 1.26.6: fixed in 1.26.6
  • 1.27.0-0 up to 1.27.0-rc.3: fixed in 1.27.0-rc.3
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
golang-1.191.19.10-1 ... 1.19.9-1 (12 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
golang-1.241.24.12-1 ... 1.24.9-1 (10 versions)
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 82× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 135 total refreshes for this CVE.

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

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Frequently asked(5)

What is CVE-2026-56865?
CVE-2026-56865 is a high vulnerability published on August 13, 2026. A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that…
When was CVE-2026-56865 disclosed?
CVE-2026-56865 was first published on August 13, 2026, with the most recent update on September 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56865 actively exploited?
CVE-2026-56865 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (2nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-56865?
CVE-2026-56865 has a CVSS v3.1 base score of 8.4 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-56865?
A fix for CVE-2026-56865 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-56865 are linked in the Vendor Advisories panel on this page.

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