httpd mod_auth directory protection bypassed by request path casing on case-insensitive filesystems (CVE-2026-73270)
Published Last modified Sources: Debian, Ubuntu, OSV, CVE.org, Msrc Update Guide, BSI
What is affected, what to do
Improper Handling of Case Sensitivity vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by requesting them with different casing, on deployments whose filesystem is case-insensitive. mod_auth:secret_path/3 decides whether a resolved filesystem path lies inside a protected directory block by running the configured directory path through re:run/3 without the caseless option. A request for /secret/file against a directory configured as /Secret therefore does not match, so the request is treated as unprotected and no authentication challenge is issued, while the filesystem resolves the differently cased path to the same file and mod_get serves it.
Update Erlang OTP to version 27.3.4.17, Erlang OTP to version 28.5.0.6, Erlang OTP to version 29.0.6.
- Affected
- Erlang OTP
lt 17.0..27.3.4.17 - Erlang OTP
lt 28.0..28.5.0.6 - Erlang OTP
lt 29.0..29.0.6 - Erlang OTP
lt 5.10..9.3.2.7 - Erlang OTP
lt 9.4..9.6.2.3 - Erlang OTP
lt 9.7..9.7.2
- Erlang OTP
- Fixed in
- Erlang OTP
27.3.4.17 - Erlang OTP
28.5.0.6 - Erlang OTP
29.0.6 - Erlang OTP
9.3.2.7 - Erlang OTP
9.6.2.3 - Erlang OTP
9.7.2
- Erlang OTP
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Metrics
8.2
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v4
8.2
CVSS v4
Severity High on the scale from 0 to 10.
Source: Debian, Ubuntu, OSV, CVE.org, Msrc Update Guide, BSI
0.9 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 60.4
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 95.39 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 8.2 Methodology
CVSS v4
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 8.2
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.9 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 60.4
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: none known · not automatable · Technical impact: partial
- Source: CISA Vulnrichment, as of 1 September 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-178
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Improper Handling of Case Sensitivity vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by requesting them with different casing, on deployments whose filesystem is case-insensitive. mod_auth:secret_path/3 decides whether a resolved filesystem path lies inside a protected directory block by running the configured directory path through re:run/3 without the caseless option. A request for /secret/file against a directory configured as /Secret therefore does not match, so the request is treated as unprotected and no authentication challenge is issued, while the filesystem resolves the differently cased path to the same file and mod_get serves it. Deployments on case-sensitive filesystems are unaffected, because there the filesystem itself rejects the mismatched casing. 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.
Source: Debian Security Advisories, Ubuntu Security Notices, OSV (Open Source Vulnerabilities), NVD (NIST), cvelistv5, Microsoft Security Update Guide, BSI WID Portal, BSI CSAF
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Erlang | OTP |
|
|
| Open Source | Erlang/OTP |
|
|
Vendors and products
Affected operating systems
| Linux | debian | erlang | trixie |
| Linux | ubuntu | erlang | bionic |
| Linux | ubuntu | erlang | focal |
| Linux | ubuntu | erlang | jammy |
| Linux | ubuntu | erlang | noble |
| Linux | ubuntu | erlang | resolute |
| Linux | ubuntu | erlang | trusty |
| Linux | ubuntu | erlang | xenial |
Weakness classes (CWE)
CWE-178Improper Handling of Case Sensitivity
Base
The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
Entry at MITRE CWE-178
References & sources
- github.comerlang/otp/security/advisories/GHSA-mh78-93cr-jx8fVendor advisory, related
- cna.erlef.orgcves/CVE-2026-73270.htmlrelated
- OSV (Open Source Vulnerabilities)vulnerability/EEF-CVE-2026-73270related
- erlang.orgdoc/system/versions.htmlx_version-scheme
- github.comerlang/otp/commit/bac19eb3dbd96cc49b6d8cabc1c04248bf8c79f6Patch
- github.comerlang/otp/commit/d8878dec0ececc2eab18e47bb18b472f224ca633Patch
- github.comerlang/otp/commit/9641944a2efbf55bea760f8ff7ba777fe3a0961cPatch
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedEEF
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/73xxx/CVE-2026-73270.json">CVE-2026-73270</a>Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: none known, automatable: no
Show the original change
Individual changes of this event as published by NVD Type Action Before After SSVC assessment added —{"id":"CVE-2026-73270","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-01T15:58:36.382951Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
ReceivedEEF
CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness type: CWE-178
Description added or changed
New references:- https://cna.erlef.org/cves/CVE-2026-73270.html
- https://github.com/erlang/otp/commit/9641944a2efbf55bea760f8ff7ba777fe3a0961c
- https://github.com/erlang/otp/commit/bac19eb3dbd96cc49b6d8cabc1c04248bf8c79f6
- https://github.com/erlang/otp/commit/d8878dec0ececc2eab18e47bb18b472f224ca633
and 3 more references
Show 11 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —Improper Handling of Case Sensitivity vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by requesting them with different casing, on deployments whose filesystem is case-insensitive. mod_auth:secret_path/3 decides whether a resolved filesystem path lies inside a protected directory block by running the configured directory path through re:run/3 without the caseless option. A request for /secret/file against a directory configured as /Secret therefore does not match, so the request is treated as unprotected and no authentication challenge is issued, while the filesystem resolves the differently cased path to the same file and mod_get serves it. Deployments on case-sensitive filesystems are unaffected, because there the filesystem itself rejects the mismatched casing. 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.CVSS added —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:XWeakness type (CWE) added —CWE-178Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/73xxx/CVE-2026-73270.json">CVE-2026-73270</a>Reference added —https://cna.erlef.org/cves/CVE-2026-73270.htmlReference added —https://github.com/erlang/otp/commit/9641944a2efbf55bea760f8ff7ba777fe3a0961cReference added —https://github.com/erlang/otp/commit/bac19eb3dbd96cc49b6d8cabc1c04248bf8c79f6Reference added —https://github.com/erlang/otp/commit/d8878dec0ececc2eab18e47bb18b472f224ca633Reference added —https://github.com/erlang/otp/security/advisories/GHSA-mh78-93cr-jx8fReference added —https://osv.dev/vulnerability/EEF-CVE-2026-73270Reference added —https://www.erlang.org/doc/system/versions.html#order-of-versionsSource identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-73270"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-73270.svg?lang=en" alt="CVE-2026-73270 – NEOSEC Intel" height="20"></a>