CVE-2026-17556Network attack vector

Unauthenticated file deletion via unsanitized request identifier

Published Aug 5, 2026 · Updated Aug 5, 2026

Path traversal in GitHub Enterprise Server 3.17.0 through 3.21.3 allows remote attackers to delete instance files via a request header. The X-GitHub-Request-Id header becomes an upload-buffer path segment without sanitization, and deferred cleanup recursively removes the traversed target. Only network reachability is required, even in private mode, and deletion can encompass user storage holding Git LFS objects, release assets, attachments, and avatars.

CVSS severity8.8
High
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in GitHub Enterprise Server 3.17.0 through 3.21.3 allows remote attackers to delete instance files via a request header. The X-GitHub-Request-Id header becomes an upload-buffer path segment without sanitization, and deferred cleanup recursively removes the traversed target. Only network reachability is required, even in private mode, and deletion can encompass user storage holding Git LFS objects, release assets, attachments, and avatars.

The record

CVE
CVE-2026-17556
Published
Aug 5, 2026
Updated
Aug 5, 2026
Vendor
Twitter
Product
GitHub Enterprise Server
Classifications
CWE-22, CAPEC-126, T1485
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.17.0 <=3.17.18 changes=[{"at":"3.17.19","status":"unaffected"}]
  2. Affected versionversion=3.18.0 <=3.18.12 changes=[{"at":"3.18.13","status":"unaffected"}]
  3. Affected versionversion=3.19.0 <=3.19.9 changes=[{"at":"3.19.10","status":"unaffected"}]
  4. Affected versionversion=3.20.0 <=3.20.5 changes=[{"at":"3.20.6","status":"unaffected"}]
  5. Affected versionversion=3.21.0 <=3.21.3 changes=[{"at":"3.21.4","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Twitter · GitHub Enterprise Serverversion=3.17.0 <=3.17.18 changes=[{"at":"3.17.19","status":"unaffected"}]; version=3.18.0 <=3.18.12 changes=[{"at":"3.18.13","status":"unaffected"}]; version=3.19.0 <=3.19.9 changes=[{"at":"3.19.10","status":"unaffected"}]; version=3.20.0 <=3.20.5 changes=[{"at":"3.20.6","status":"unaffected"}]; version=3.21.0 <=3.21.3 changes=[{"at":"3.21.4","status":"unaffected"}]

Published CVSS scores

8.8GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
8.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CAPEC-126Path Traversal
T1485Data Destruction

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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