Cross-origin file overwrite via unprotected PUT
Published May 4, 2026 · Updated May 4, 2026
CSRF in goshs before 2.0.2 allows remote attackers to write or overwrite webroot files through a victim's browser. The PUT handler in httpserver/updown.go omits checkCSRF, while the OPTIONS handler in httpserver/server.go permits every origin to issue PUT requests. Exploitation requires a victim to visit attacker-controlled content that can reach an open, write-enabled goshs server; the result is file creation or silent replacement, including across localhost or internal-network boundaries.
Summary
What happened
CSRF in goshs before 2.0.2 allows remote attackers to write or overwrite webroot files through a victim's browser. The PUT handler in httpserver/updown.go omits checkCSRF, while the OPTIONS handler in httpserver/server.go permits every origin to issue PUT requests. Exploitation requires a victim to visit attacker-controlled content that can reach an open, write-enabled goshs server; the result is file creation or silent replacement, including across localhost or internal-network boundaries.
The record
- CVE
- CVE-2026-42091
- Published
- May 4, 2026
- Updated
- May 4, 2026
- Vendor
- Patrick Hener
- Product
- goshs
- Classifications
- CWE-352, CAPEC-62, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 4, 2026CVE publishedPublication date reported by the CVE source.
- May 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.0.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Upstream cross-origin PUT proof of conceptproof of concept · demonstrated
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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