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TI-2026-47459 Aliases CVE-2026-66835

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

Priority LOW 38CWE-50Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00973 62nd percentileScored 2026-11-07
Fix Fixed OTP (Erlang): 27.3.4.17, 28.5.0.6, 29.0.6 +3Red Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ErlangOTP17.0 to before 27.3.4.17; 28.0 to before 28.5.0.6; 29.0 to before 29.0.627.3.4.17, 28.5.0.6, 29.0.6Patch availableCNA
ErlangOTP5.10 to before 9.3.2.7; 9.4 to before 9.6.2.3; 9.7 to before 9.7.29.3.2.7, 9.6.2.3, 9.7.2Patch availableCNA
  • OTP VendorErlang Affected 17.0 to before 27.3.4.17; 28.0 to before 28.5.0.6; 29.0 to before 29.0.6 Fixed in 27.3.4.17, 28.5.0.6, 29.0.6 Patch available CNA
  • OTP VendorErlang Affected 5.10 to before 9.3.2.7; 9.4 to before 9.6.2.3; 9.7 to before 9.7.2 Fixed in 9.3.2.7, 9.6.2.3, 9.7.2 Patch available CNA

CPE names CNA · 1

CPEVersionsRoleVendor
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*——Erlang
  • cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:* Versions — — ·Erlang

Remediation

  • Fix · CNA OTP (Erlang) Fixed in 27.3.4.17, 28.5.0.6, 29.0.6
  • Fix · CNA OTP (Erlang) Fixed in 9.3.2.7, 9.6.2.3, 9.7.2

Red Hat 1 advisory

  • RHSA-2026:62531 Released 2026-09-02 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images erlang27-27.3.4.17-0.1.hum1@aarch64, erlang27-27.3.4.17-0.1.hum1@src, erlang27-27.3.4.17-0.1.hum1@x86_64 +47

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Erlang OTP 17.0, 27.3.4.17 and 2 more versions

    11 records Highest priority Priority MEDIUM 2 MEDIUM, 9 LOW

    Other records, highest priority first

    • TI-2026-50021 httpd applies no timeout while receiving a request body, parking a worker on a stalled clientPriority MEDIUM 45
    • TI-2026-52570 inets,httpd: Memory Exhaustion via Unenforced max_body_size During Chunked Body ReceptionPriority MEDIUM 44
    • TI-2026-52886 Heap-based buffer overflow in Erlang OTPPriority LOW 37
    Show all 11 records →
  • Release ·

    Erlang OTP 5.10, 9.3.2.7 and 2 more versions

    9 records Highest priority Priority MEDIUM 2 MEDIUM, 7 LOW

    Other records, highest priority first

    • TI-2026-50021 httpd applies no timeout while receiving a request body, parking a worker on a stalled clientPriority MEDIUM 45
    • TI-2026-52570 inets,httpd: Memory Exhaustion via Unenforced max_body_size During Chunked Body ReceptionPriority MEDIUM 44
    • TI-2026-51857 inets, httpd: HTTP Request Smuggling via Transfer-Encoding and Content-LengthPriority LOW 37
    Show all 9 records →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Hardened ImagesFixed RHSA-2026:62531

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-66835

References

Patch 3

Advisory 1

Other 3

  • TI-2025-23504 Erlang/OTP SSH Vulnerable to Pre-Authentication RCE KEVCVSS 3.1CRITICAL 10.0
  • TI-2026-48954 httpd parks a request worker indefinitely on a malformed chunk size sent after the headers CVSS 4.0HIGH 8.7
  • TI-2023-26623 The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6… CVSS 3.1MEDIUM 5.9
  • TI-2026-71037 Path traversal in rebar3 via unvalidated dependency app names CVSS 4.0HIGH 7.5
  • TI-2024-36042 ssl fails to validate incorrect extened key usage CVSS 3.1MEDIUM 5.5
  • TI-2020-10791 Rebar3 versions 3.0.0-beta.3 to 3.13.2 are vulnerable to OS command injection via URL… CVSS 3.1CRITICAL 9.8
See all 80 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences