CVE-2026-66835 (GCVE-0-2026-66835)
Vulnerability from cvelistv5
Published
2026-09-01 14:49
Modified
2026-09-08 01:08
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-50 - Path Equivalence: '//multiple/leading/slash'
Summary
Path Equivalence vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by prefixing the request path with an extra slash.
httpd_request:validate_uri/1 normalises the request URI with uri_string:normalize/1, which performs RFC 3986 dot-segment removal but does not collapse empty path segments, so a doubled slash survives. mod_alias:real_name/3 concatenates the document root with that URI, and mod_auth:secret_path/3 then decides whether the result lies inside a protected directory block by running the configured directory path as an unanchored regular expression against it. The doubled slash breaks the contiguous substring the regex needs, so the request is treated as unprotected and no authentication challenge is issued, while mod_get opens the same path and the operating system collapses the doubled slash and returns the protected file. The same path mismatch also evades the per-path accounting in mod_security.
This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.
References
Impacted products
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\"lib/inets/src/http_server/httpd_request.erl\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"mod_auth:secret_path/3\"}, {\"name\": \"mod_alias:real_name/3\"}, {\"name\": \"httpd_request:validate_uri/1\"}]}], \"references\": [{\"url\": \"https://github.com/erlang/otp/security/advisories/GHSA-r4vv-vc2c-2fw6\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-66835.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-66835\", \"tags\": [\"related\"]}, {\"url\": \"https://www.erlang.org/doc/system/versions.html#order-of-versions\", \"tags\": [\"x_version-scheme\"]}, {\"url\": \"https://github.com/erlang/otp/commit/bac19eb3dbd96cc49b6d8cabc1c04248bf8c79f6\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/erlang/otp/commit/d8878dec0ececc2eab18e47bb18b472f224ca633\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/erlang/otp/commit/9641944a2efbf55bea760f8ff7ba777fe3a0961c\", \"tags\": [\"patch\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Path Equivalence vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by prefixing the request path with an extra slash.\\n\\nhttpd_request:validate_uri/1 normalises the request URI with uri_string:normalize/1, which performs RFC 3986 dot-segment removal but does not collapse empty path segments, so a doubled slash survives. mod_alias:real_name/3 concatenates the document root with that URI, and mod_auth:secret_path/3 then decides whether the result lies inside a protected directory block by running the configured directory path as an unanchored regular expression against it. The doubled slash breaks the contiguous substring the regex needs, so the request is treated as unprotected and no authentication challenge is issued, while mod_get opens the same path and the operating system collapses the doubled slash and returns the protected file. The same path mismatch also evades the per-path accounting in mod_security.\\n\\nThis issue affects OTP from OTP\\u00a017.0 before OTP\\u00a027.3.4.17, from OTP\\u00a028.0 before OTP\\u00a028.5.0.6, and from OTP\\u00a029.0 before OTP\\u00a029.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP\\u00a017.0, corresponding to inets before 5.10, is affected is unknown.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003ePath Equivalence vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a \u003ccode\u003emod_auth\u003c/code\u003e protected directory by prefixing the request path with an extra slash.\u003c/p\u003e\\n\u003cp\u003e\u003ccode\u003ehttpd_request:validate_uri/1\u003c/code\u003e normalises the request URI with \u003ccode\u003euri_string:normalize/1\u003c/code\u003e, which performs RFC 3986 dot-segment removal but does not collapse empty path segments, so a doubled slash survives. \u003ccode\u003emod_alias:real_name/3\u003c/code\u003e concatenates the document root with that URI, and \u003ccode\u003emod_auth:secret_path/3\u003c/code\u003e then decides whether the result lies inside a protected \u003ccode\u003edirectory\u003c/code\u003e block by running the configured directory path as an unanchored regular expression against it. The doubled slash breaks the contiguous substring the regex needs, so the request is treated as unprotected and no authentication challenge is issued, while \u003ccode\u003emod_get\u003c/code\u003e opens the same path and the operating system collapses the doubled slash and returns the protected file. The same path mismatch also evades the per-path accounting in \u003ccode\u003emod_security\u003c/code\u003e.\u003c/p\u003e\\n\u003cp\u003eThis issue affects OTP from OTP\u0026nbsp;17.0 before OTP\u0026nbsp;27.3.4.17, from OTP\u0026nbsp;28.0 before OTP\u0026nbsp;28.5.0.6, and from OTP\u0026nbsp;29.0 before OTP\u0026nbsp;29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP\u0026nbsp;17.0, corresponding to inets before 5.10, is affected is unknown.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Path Equivalence vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a `mod_auth` protected directory by prefixing the request path with an extra slash.\\n\\n`httpd_request:validate_uri/1` normalises the request URI with `uri_string:normalize/1`, which performs RFC 3986 dot-segment removal but does not collapse empty path segments, so a doubled slash survives. `mod_alias:real_name/3` concatenates the document root with that URI, and `mod_auth:secret_path/3` then decides whether the result lies inside a protected `directory` block by running the configured directory path as an unanchored regular expression against it. The doubled slash breaks the contiguous substring the regex needs, so the request is treated as unprotected and no authentication challenge is issued, while `mod_get` opens the same path and the operating system collapses the doubled slash and returns the protected file. The same path mismatch also evades the per-path accounting in `mod_security`.\\n\\nThis issue affects OTP from OTP\\u00a017.0 before OTP\\u00a027.3.4.17, from OTP\\u00a028.0 before OTP\\u00a028.5.0.6, and from OTP\\u00a029.0 before OTP\\u00a029.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP\\u00a017.0, corresponding to inets before 5.10, is affected is unknown.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-50\", \"description\": \"CWE-50 Path Equivalence: \u0027//multiple/leading/slash\u0027\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"Only servers that protect a directory with mod_auth, by configuring a directory block with authentication requirements, are affected. A server that serves no authenticated directory has no protection for this issue to bypass.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eOnly servers that protect a directory with \u003ccode\u003emod_auth\u003c/code\u003e, by configuring a \u003ccode\u003edirectory\u003c/code\u003e block with authentication requirements, are affected. A server that serves no authenticated directory has no protection for this issue to bypass.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Only servers that protect a directory with `mod_auth`, by configuring a `directory` block with authentication requirements, are affected. A server that serves no authenticated directory has no protection for this issue to bypass.\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"27.3.4.17\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"28.5.0.6\", \"versionStartIncluding\": \"28.0\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"29.0.6\", \"versionStartIncluding\": \"29.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-08T01:08:16.964Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-66835\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-08T01:08:16.964Z\", \"dateReserved\": \"2026-08-17T12:00:02.063Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-09-01T14:49:47.805Z\", \"assignerShortName\": \"EEF\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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