CVE-2026-17556

CRITICALNVD 9.19.1—
EchelonGraph scoreHIGH 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 — 4 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: 1%CVSS: 9.1Exploit: None knownExposed: 0

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

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
9.1(high)
EG Risk
56(Track)
EG Risk 56/100SSVC: Track

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%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
41%
KEV
Not listed

Published

August 5, 2026

Last Modified

August 18, 2026

Advisory Details (5)

Auto-updated Aug 5, 2026
No patch confirmed yet.
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 42× in last 7d / 76× 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.

  1. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-20 22:16 UTCGHSA enrichment
  3. 2026-08-20 18:36 UTCGHSA enrichment
  4. 2026-08-20 14:55 UTCGHSA enrichment
  5. 2026-08-20 11:10 UTCGHSA enrichment
  6. 2026-08-20 07:30 UTCGHSA enrichment
  7. 2026-08-20 03:50 UTCGHSA enrichment
  8. 2026-08-20 00:06 UTCGHSA enrichment
  9. 2026-08-19 20:26 UTCEG score recompute
  10. 2026-08-19 20:26 UTCGHSA enrichment
  11. 2026-08-19 17:03 UTCEPSS rescore
  12. 2026-08-19 16:42 UTCGHSA enrichment
  13. 2026-08-19 12:57 UTCGHSA enrichment
  14. 2026-08-19 09:15 UTCGHSA enrichment
  15. 2026-08-19 05:35 UTCGHSA enrichment
  16. 2026-08-19 01:55 UTCGHSA enrichment
  17. 2026-08-18 22:14 UTCEG score recompute
  18. 2026-08-18 22:14 UTCGHSA enrichment
  19. 2026-08-18 18:25 UTCEG score recompute▲ 0.30
  20. 2026-08-18 18:25 UTCGHSA enrichment
  21. 2026-08-18 18:22 UTCNVD updateCVSS v3 → 9.1 · severity → CRITICAL
  22. 2026-08-18 15:34 UTCEG score recompute
  23. 2026-08-18 15:34 UTCGHSA enrichment
  24. 2026-08-18 13:48 UTCEPSS rescore
  25. 2026-08-18 13:18 UTCGHSA enrichment
Show 51 more
  1. 2026-08-18 00:15 UTCEG score recompute
  2. 2026-08-18 00:15 UTCGHSA enrichment
  3. 2026-08-17 13:47 UTCEPSS rescore
  4. 2026-08-17 11:04 UTCGHSA enrichment
  5. 2026-08-16 22:02 UTCEG score recompute
  6. 2026-08-16 22:02 UTCGHSA enrichment
  7. 2026-08-16 14:56 UTCEPSS rescore
  8. 2026-08-16 08:59 UTCEG score recompute
  9. 2026-08-16 08:59 UTCGHSA enrichment
  10. 2026-08-16 02:14 UTCEPSS rescore
  11. 2026-08-15 19:57 UTCGHSA enrichment
  12. 2026-08-15 06:54 UTCEG score recompute
  13. 2026-08-15 06:54 UTCGHSA enrichment
  14. 2026-08-15 01:30 UTCEPSS rescore
  15. 2026-08-14 17:51 UTCGHSA enrichment
  16. 2026-08-14 04:49 UTCEG score recompute
  17. 2026-08-14 04:49 UTCGHSA enrichment
  18. 2026-08-13 22:00 UTCEPSS rescore
  19. 2026-08-13 15:46 UTCGHSA enrichment
  20. 2026-08-13 02:44 UTCEG score recompute
  21. 2026-08-13 02:44 UTCGHSA enrichment
  22. 2026-08-12 13:50 UTCEPSS rescore
  23. 2026-08-12 13:42 UTCGHSA enrichment
  24. 2026-08-12 00:39 UTCEG score recompute
  25. 2026-08-12 00:39 UTCGHSA enrichment
  26. 2026-08-11 13:42 UTCEPSS rescore
  27. 2026-08-11 11:37 UTCEG score recompute
  28. 2026-08-11 11:37 UTCGHSA enrichment
  29. 2026-08-11 00:00 UTCEPSS rescore
  30. 2026-08-10 22:35 UTCGHSA enrichment
  31. 2026-08-10 09:32 UTCGHSA enrichment
  32. 2026-08-09 20:30 UTCEG score recompute
  33. 2026-08-09 20:30 UTCGHSA enrichment
  34. 2026-08-09 13:46 UTCEPSS rescore
  35. 2026-08-09 07:28 UTCGHSA enrichment
  36. 2026-08-08 18:26 UTCEG score recompute
  37. 2026-08-08 18:26 UTCGHSA enrichment
  38. 2026-08-08 16:37 UTCEPSS rescore
  39. 2026-08-08 05:24 UTCEG score recompute
  40. 2026-08-08 05:24 UTCGHSA enrichment
  41. 2026-08-07 16:21 UTCGHSA enrichment
  42. 2026-08-07 03:19 UTCGHSA enrichment
  43. 2026-08-06 14:17 UTCEG score recompute
  44. 2026-08-06 14:17 UTCGHSA enrichment
  45. 2026-08-06 13:54 UTCEG score recompute
  46. 2026-08-06 13:54 UTCGHSA enrichment
  47. 2026-08-06 13:46 UTCEPSS rescore
  48. 2026-08-06 09:34 UTCGHSA enrichment
  49. 2026-08-05 20:32 UTCEG score recompute
  50. 2026-08-05 20:15 UTCEG score recompute
  51. 2026-08-05 20:15 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

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 in the National Vulnerability Database 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 1% probability of exploitation in the next 30 days, which ranks it in the top 59.1% of all 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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-17556, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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