Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-17556 – Unauthenticated Path Traversal / Arbitrary File Deletion – GitHub Enterprise Server

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-17556 is an unauthenticated path traversal vulnerability (CWE-22) in GitHub Enterprise Server that allows a remote attacker to delete arbitrary files and directories on the instance. Because exploitation requires no authentication or user interaction and can be triggered over the network, the issue is rated HIGH severity (CVSS 8.8).

Technical details

  • Root cause: The X-GitHub-Request-Id HTTP header was used unsanitized as a filesystem path segment for upload buffers, allowing path traversal sequences to escape the intended directory.
  • Trigger conditions: An attacker sends a crafted request supplying a malicious X-GitHub-Request-Id header value; no credentials or special privileges are needed.
  • Attack vector: Network (remote), low complexity, no authentication, no user interaction.
  • Impact: Arbitrary file and directory deletion, including storage directories holding Git LFS objects, release assets, attachments, and avatars — causing loss of integrity and availability of stored data.

Affected software

  • GitHub Enterprise Server 3.17.0 through 3.17.18 (fixed in 3.17.19)
  • GitHub Enterprise Server 3.18.0 through 3.18.12 (fixed in 3.18.13)
  • GitHub Enterprise Server 3.19.0 through 3.19.9 (fixed in 3.19.10)
  • GitHub Enterprise Server 3.20.0 through 3.20.5 (fixed in 3.20.6)
  • GitHub Enterprise Server 3.21.0 through 3.21.3 (fixed in 3.21.4)

Severity

CVSS v4.0 base score: 8.8 (HIGH)
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade GitHub Enterprise Server to a fixed release for your branch — 3.17.19, 3.18.13, 3.19.10, 3.20.6, or 3.21.4.
  • If no patch can be applied immediately: Restrict network access to the GitHub Enterprise Server instance to trusted networks, and place it behind a proxy or WAF that strips or validates the X-GitHub-Request-Id request header before it reaches the application.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Set-Cookie response header: _fi_sess
  • Raw response body: _fi_sess

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge