CVE-2026-100409

Published

15 October 2026

Modified

15 October 2026

CVSS Score v3.1 7.5

Click a component to see what it means

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Score 0.0031 22th percentile

Risk Priority 56 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-100409 is a high-severity Hex Encoding (CWE-177) vulnerability. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Steganography (T1001.002); ranked at the 22th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-102200

Vulnerability Data

OpenNext Cloudflare is an open Next.js adapter for Cloudflare. From 0.3.0 until 1.20.2, applications that enable enableCacheInterception, rely on middleware for access control, and have a matching cached protected route process encoded pathnames inconsistently between middleware matching and cache lookup.…

An unauthenticated attacker can use a percent-encoded pathname that does not match authorization middleware but decodes to the cache key of a protected route, causing cached content to be returned without authorization. Malformed encodings can also be partially decoded, allowing cache lookup to continue with a pathname that middleware did not evaluate consistently. This issue is fixed in version 1.20.2.

CWE(s): CWE-177 CWE-180

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001.002 Steganography Command And Control

Adversaries may use steganographic techniques to hide command and control traffic to make detection efforts more difficult.

attack.mitre.org →

T1003 OS Credential Dumping Credential Access

Adversaries may attempt to dump credentials to obtain account login and credential material, normally in the form of a hash or a clear text password.

attack.mitre.org →

T1003.003 NTDS Credential Access

Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights.

attack.mitre.org →

T1003.004 LSA Secrets Credential Access

Adversaries with SYSTEM access to a host may attempt to access Local Security Authority (LSA) secrets, which can contain a variety of different credential materials, such as credentials for service accounts.

attack.mitre.org →

T1003.008 /etc/passwd and /etc/shadow Credential Access

Adversaries may attempt to dump the contents of <code>/etc/passwd</code> and <code>/etc/shadow</code> to enable offline password cracking.

attack.mitre.org →

T1005 Data from Local System Collection

Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

Affected Assets

Mitigating Controls

Control response

Prevent

Stop it (NIST 800-53)

—

Detect

Catch it (NIST detect / respond)

—

Harden

Shrink the surface (DISA STIG)

—

Validate

Prove the fix (OWASP ASVS)

V1.3.8
V1.2.2
V1.1.1
V12.1.3

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 partial match

blocks

Secure SDLC practices directly require correct URL-encoding/decoding and input validation during development.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match

removes

A.8.1 User end point devices partial match

removes

A.8.19 Installation of software on operational systems partial match

removes

A.8.25 Secure development life cycle partial match

blocks

Secure SDLC processes include validation steps that reduce CWE-177, yet the control is broader than this single weakness.

A.8.26 Application security requirements partial match

blocks

Application security requirements explicitly call for input validation and canonicalization, directly preventing improper URL decoding.