httpd mod_auth directory protection bypassed by a doubled slash in the request path

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-66835
StatePUBLISHED
AssignerEEF
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-01 15:17:23 UTC
Updated2026-09-08 01:17:52 UTC
DescriptionPath 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.

Risk And Classification

Primary CVSS: v4.0 8.2 HIGH from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.006350000 probability, percentile 0.480730000 (date 2026-09-03)

Problem Types: CWE-50 | CWE-50 CWE-50 Path Equivalence: '//multiple/leading/slash'

VersionSourceTypeScoreSeverityVector
4.06b3ad84c-e1a6-4bf7-a703-f496b71e49dbSecondary8.2HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS8.2HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Erlang OTP unknown 17.0 otp Not specified
CNA Erlang OTP affected 17.0 27.3.4.17 otp Not specified
CNA Erlang OTP affected 28.0 28.5.0.6 otp Not specified
CNA Erlang OTP affected 29.0 29.0.6 otp Not specified
CNA Erlang OTP unknown 5.10 otp Not specified
CNA Erlang OTP affected 5.10 9.3.2.7 otp Not specified
CNA Erlang OTP affected 9.4 9.6.2.3 otp Not specified
CNA Erlang OTP affected 9.7 9.7.2 otp Not specified
CNA Erlang OTP affected 84adefa331c4159d432d22840663c38f155cd4c1 * git Not specified

References

ReferenceSourceLinkTags
github.com/erlang/otp/commit/d8878dec0ececc2eab18e47bb18b472f224ca633 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/erlang/otp/commit/9641944a2efbf55bea760f8ff7ba777fe3a0961c 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/erlang/otp/commit/bac19eb3dbd96cc49b6d8cabc1c04248bf8c79f6 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
www.erlang.org/doc/system/versions.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db www.erlang.org
github.com/erlang/otp/security/advisories/GHSA-r4vv-vc2c-2fw6 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
cna.erlef.org/cves/CVE-2026-66835.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db cna.erlef.org
osv.dev/vulnerability/EEF-CVE-2026-66835 6b3ad84c-e1a6-4bf7-a703-f496b71e49db osv.dev
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Arthur Chan / Ada Logics (en)

CNA: David Korczynski / Ada Logics (en)

CNA: Adam Korczynski / Ada Logics (en)

CNA: Konrad Pietrzak / Ericsson (en)

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