CVE-2026-17556

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: HIGH) published 2026-08-05. NVD baseline CVSS 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.8%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The X-GitHub-Request-Id request header was used without sanitization as a filesystem path segment for the upload buffer directory, so a traversal value pointed the buffer at an arbitrary path and the deferred cleanup routine recursively removed the traversed target. Exploitation required only network reachability to the instance and no authentication, and it worked even when private mode was enabled. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.4, 3.20.6, 3.19.10, 3.18.13 and 3.17.19. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100CISA 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
Severity91% × 45%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
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
0.8%
EPSS %ILE
55th
KEV
Not listed

CISA SSVCTrack 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). 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 5, 2026

Last Modified

August 18, 2026

Advisory Details (5)

Auto-updated Sep 15, 2026
Fix named in the CVE record.
generic

Release notes - GitHub Enterprise Server 3.21 Docs

https://docs.github.com/en/[email protected]/admin/release-notes#3.21.4
generic

Release notes - GitHub Enterprise Server 3.20 Docs

https://docs.github.com/en/[email protected]/admin/release-notes#3.20.6
generic

Release notes - GitHub Enterprise Server 3.19 Docs

https://docs.github.com/en/[email protected]/admin/release-notes#3.19.10
generic

Release notes - GitHub Enterprise Server 3.18 Docs

https://docs.github.com/en/[email protected]/admin/release-notes#3.18.13
generic

Release notes - GitHub Enterprise Server 3.17 Docs

https://docs.github.com/en/[email protected]/admin/release-notes#3.17.19

Vendor Advisories for CVE-2026-17556(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 23× in last 7d / 149× 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 328 total refreshes for this CVE.

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

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Frequently asked(5)

What is CVE-2026-17556?
CVE-2026-17556 is a critical vulnerability published on August 5, 2026. A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The…
When was CVE-2026-17556 disclosed?
CVE-2026-17556 was first published on August 5, 2026, with the most recent update on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-17556 actively exploited?
CVE-2026-17556 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.8% probability of exploitation in the next 30 days (55th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-17556?
CVE-2026-17556 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-17556?
A fix for CVE-2026-17556 is available — its CVE record says: "This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.4, 3.20.6, 3.19.10, 3.18.13 and 3.17.19." The vendor advisories EchelonGraph has for CVE-2026-17556 are linked in the Vendor Advisories panel on this page.

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