CVE-2026-50638: Perl DogStatsd Metric Injection Vulnerability

CVE-2026-50638 Overview

CVE-2026-50638 affects Metrics::Any::Adapter::DogStatsd versions before 0.04 for Perl. The module fails to sanitize metric names and tag values before transmitting them over the statsd or dogstatsd protocol. The statsd protocol allows multiple metrics per packet, separated by newlines. Attackers can inject crafted newline characters and statsd control characters into metric data to forge or alter additional metrics. The _tags function compounds the issue by not validating tag values for newlines or protocol delimiters. This weakness is classified under CWE-93: Improper Neutralization of CRLF Sequences. The module extends Metrics::Any::Adapter::Statsd, which carries a related vulnerability tracked separately.

Critical Impact
Attackers who control metric names or tag values can inject arbitrary statsd metrics, corrupting monitoring data and enabling downstream alert evasion or false telemetry.

Affected Products

Metrics::Any::Adapter::DogStatsd for Perl, versions before 0.04
Applications using Metrics::Any::Adapter::Statsd (related CVE-2026-50637)
Perl applications that forward user-influenced data into metric names or tags

Discovery Timeline

2026-06-10 - CVE-2026-50638 published to NVD
2026-06-10 - Last updated in NVD database

Technical Details for CVE-2026-50638

Vulnerability Analysis

The statsd wire protocol and the dogstatsd extension transmit metrics as plaintext UDP payloads. A single packet may contain multiple metrics separated by the newline character (\n). Metrics::Any::Adapter::DogStatsd constructs these payloads by interpolating caller-supplied strings for metric names and tag values directly into the protocol payload. The library performs no neutralization of newline or statsd control characters before transmission.

When any portion of a metric name or tag derives from untrusted input, an attacker can embed a newline followed by an attacker-chosen metric. The downstream collector treats the injected segment as an independent, fully formed metric. This leads to falsified counters, fabricated timing data, or suppression of legitimate alerts driven by metric thresholds.

Root Cause

The root cause is missing input neutralization in the metric emission path. The _tags helper concatenates tag keys and values into the comma-delimited dogstatsd tag section without rejecting or escaping \n, \r, |, or : characters. The metric name path exhibits the same gap. Because the protocol uses these characters as structural delimiters, unfiltered input directly corrupts protocol framing — the canonical pattern in [CWE-93].

Attack Vector

Exploitation requires that an attacker influence a string passed to the metric or tag API. Common sources include HTTP headers, usernames, URL paths, or any field a developer instruments without sanitization. The attacker supplies a value containing a newline followed by a forged metric line, for example a counter increment for a fictitious key. When the adapter emits the packet, the receiving statsd or Datadog agent parses the injected line as a legitimate metric. Tag-channel exploitation follows the same pattern using the comma and pipe delimiters in addition to newlines.

No public proof-of-concept code is referenced in the advisory. See the MetaCPAN release notes for the upstream fix description.

Detection Methods for CVE-2026-50638

Indicators of Compromise

Unexpected metric names appearing in statsd or Datadog dashboards that do not correspond to any instrumented code path
Metric tag values containing newline, carriage return, or pipe characters in raw collector logs
Sudden spikes or drops in counters that align with periods of untrusted user activity rather than application traffic

Detection Strategies

Audit Perl source for calls into Metrics::Any::Adapter::DogStatsd and trace whether metric names or tag values originate from request-bound data
Enable verbose logging on the receiving statsd or dogstatsd agent and grep payloads for embedded \n, \r, or stray | and : sequences inside tag positions
Compare the set of metric names emitted in production against the static set declared in code; flag any deviation

Monitoring Recommendations

Forward statsd agent access logs into a centralized logging platform and alert on metric names not present in an allowlist
Track the cardinality of tag values per metric; metric injection typically inflates cardinality with one-off, malformed values
Correlate anomalous metric emission with application request logs to identify the originating input field

How to Mitigate CVE-2026-50638

Immediate Actions Required

Upgrade Metrics::Any::Adapter::DogStatsd to version 0.04 or later across all Perl deployments
Upgrade Metrics::Any::Adapter::Statsd in parallel to address the related CVE-2026-50637
Inventory every call site that emits metrics with attacker-influenceable strings and add server-side validation

Patch Information

The maintainer addressed the issue in Metrics::Any::Adapter::Statsd version 0.04, which the DogStatsd adapter inherits. The fix introduces neutralization of newline and statsd control characters in both metric names and tags. Refer to the MetaCPAN release changes and the related CVE-2026-50637 record for the upstream advisory.

Workarounds

Wrap metric and tag arguments in an application-level sanitizer that strips or rejects \n, \r, |, :, and , before they reach the adapter
Restrict metric names to a static allowlist defined at code level rather than deriving names from runtime input
Apply ingress filtering on the statsd or dogstatsd UDP socket to drop packets from sources outside the application tier

bash

# Configuration example: pin the fixed version in cpanfile
requires 'Metrics::Any::Adapter::DogStatsd', '>= 0.04';
requires 'Metrics::Any::Adapter::Statsd',    '>= 0.04';

# Then refresh dependencies
cpanm --installdeps .