CVE-2026-30852

HighPublic PoC

Published: 07 March 2026

Published

07 March 2026

Modified

11 March 2026

KEV Added

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Patch

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CVSS Score 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Score 0.0006 17.9th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-30852 is a high-severity Injection (CWE-74) vulnerability in Caddyserver Caddy. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 17.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques.

Threat & Defense Details

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

AC-15 Automated Marking

addresses: CWE-200

Automated marking applies security attributes to system outputs, making it harder for attackers to exploit unmarked sensitive information leading to unauthorized exposure.

AC-16 Security and Privacy Attributes

addresses: CWE-200

Proper attribute retention and permitted-value enforcement limits unauthorized actors from accessing sensitive information lacking correct labels.

AC-20 Use of External Systems

addresses: CWE-200

Prevents unauthorized exposure of sensitive information by prohibiting untrusted external systems from processing or storing it.

AC-21 Information Sharing

addresses: CWE-200

By enforcing authorization matching prior to sharing, the control reduces the risk of exposing sensitive information to unauthorized actors.

AC-22 Publicly Accessible Content

addresses: CWE-200

Review and removal of nonpublic information from publicly accessible systems directly prevents exposure of sensitive data to unauthorized actors.

AC-23 Data Mining Protection

addresses: CWE-200

Data mining protection mechanisms detect and block unauthorized bulk extraction of sensitive data, directly mitigating exposure to unauthorized actors.

AT-2 Literacy Training and Awareness

addresses: CWE-200

Literacy training teaches users to recognize and avoid actions that result in unauthorized exposure of sensitive information.

AT-4 Training Records

addresses: CWE-200

Retaining and monitoring training records confirms personnel have completed privacy and security awareness training on handling sensitive data, reducing the chance of unauthorized exposure due to lack of knowledge.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

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 →

T1552 Unsecured Credentials Credential Access

Adversaries may search compromised systems to find and obtain insecurely stored credentials.

attack.mitre.org →

Why these techniques?

Remote unauthenticated exploitation of public-facing Caddy server via crafted headers (T1190) directly enables arbitrary local file reads and environment variable disclosure (T1005, T1552).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Caddy is an extensible server platform that uses TLS by default. From version 2.7.5 to before version 2.11.2, the vars_regexp matcher in vars.go:337 double-expands user-controlled input through the Caddy replacer. When vars_regexp matches against a placeholder like {http.request.header.X-Input}, the header…

value gets resolved once (expected), then passed through repl.ReplaceAll() again (the bug). This means an attacker can put {env.DATABASE_URL} or {file./etc/passwd} in a request header and the server will evaluate it, leaking environment variables, file contents, and system info. This issue has been patched in version 2.11.2.

Deeper analysisAI

CVE-2026-30852 is a vulnerability in Caddy, an extensible server platform that uses TLS by default, affecting versions from 2.7.5 up to but not including 2.11.2. The issue resides in the vars_regexp matcher at vars.go:337, where user-controlled input is double-expanded through the Caddy replacer. Specifically, when the matcher processes a placeholder such as {http.request.header.X-Input}, the header value is resolved once as expected but then passed through repl.ReplaceAll() again, enabling unintended evaluation of embedded placeholders.

The vulnerability can be exploited by any unauthenticated remote attacker with network access, requiring low complexity and no user interaction (CVSS 7.5: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N). By injecting placeholders like {env.DATABASE_URL} or {file./etc/passwd} into a request header such as X-Input, the attacker triggers the double expansion, allowing the server to evaluate and disclose sensitive environment variables, file contents, and system information.

Mitigation is available via the patch in Caddy version 2.11.2, as detailed in the project's security advisory (GHSA-m2w3-8f23-hxxf), the corresponding pull request (https://github.com/caddyserver/caddy/pull/5408), and the release notes (https://github.com/caddyserver/caddy/releases/tag/v2.11.2). Security practitioners should upgrade affected instances immediately to prevent information disclosure associated with CWE-74 (injection) and CWE-200 (exposure of sensitive information).