CVE-2026-115824 in Starman
Summary
by MITRE • 10/25/2026
Starman versions before 0.4019 for Perl allow memory exhaustion via unbounded buffering of chunked request bodies.
The chunked body decoder keeps each chunk in memory until the whole chunk and its CRLF have arrived, and sets no limit on the length of a chunk-size line. A client that declares a huge chunk size and streams data, or sends a chunk-size line that never ends, grows the buffer for as long as it keeps sending.
A remote attacker can exhaust worker memory with a single connection.
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Analysis
by VulDB Data Team • 10/25/2026
The vulnerability identified in Starman versions prior to 0.4019 represents a critical resource exhaustion flaw rooted in the improper handling of HTTP chunked transfer encoding within the Perl-based web server environment. This issue specifically affects the internal mechanism responsible for decoding chunked request bodies, which is a standard method used by clients to send data of unknown size without pre-allocating memory for the entire payload. The core technical deficiency lies in the decoder's logic, which retains each individual chunk in system memory until both the complete chunk body and its terminating Carriage Return Line Feed sequence are fully received. Crucially, there is no upper bound or validation applied to the length of the chunk-size line itself, nor is there a limit on the cumulative size of chunks held in buffer during processing. This architectural oversight creates a direct pathway for malicious actors to exploit the server's memory allocation routines through unbounded buffering operations that consume resources indefinitely as long as data transmission continues.
From an operational perspective, this flaw enables a remote attacker to execute a Denial of Service attack with minimal effort and resource expenditure on their end. By establishing a single connection to the vulnerable Starman instance, an adversary can declare an arbitrarily large chunk size in the HTTP header or stream data indefinitely while keeping the connection open. Because the server attempts to buffer these chunks in memory without enforcing any maximum limits, the worker process responsible for handling that specific request will continuously allocate more RAM. This behavior leads to rapid and severe memory exhaustion on the host system. As available memory is depleted, not only does the targeted application become unresponsive, but other services running on the same server may also suffer from performance degradation or crash due to insufficient resources. The impact is particularly acute because it requires only one connection per worker process to trigger the condition, allowing an attacker with limited bandwidth to overwhelm a high-performance web server infrastructure.
This vulnerability aligns closely with Common Weakness Enumeration category CWE-400, which describes Uncontrolled Resource Consumption, and more specifically relates to issues involving unbounded buffers or lack of input validation regarding data size limits. In terms of the MITRE ATT&CK framework, this exploit technique falls under the Tactic Impact, specifically within the subtechnique for Denial of Service via resource exhaustion. The attack vector is classified as Remote (Network) with Low Complexity, indicating that it can be automated and does not require authentication or sophisticated social engineering to succeed. The persistence of this flaw in older versions highlights a common challenge in maintaining legacy Perl-based web server configurations where default buffer limits are either absent or set too high for production environments facing untrusted input streams.
To mitigate this vulnerability, organizations must immediately upgrade Starman to version 0.4019 or later, as the release notes indicate that these bounds have been implemented to prevent such memory exhaustion scenarios. For systems unable to update immediately due to dependency constraints, temporary mitigations should focus on placing a reverse proxy in front of the Starman instance capable of enforcing strict request body size limits and chunked encoding validation. Tools like Nginx or Apache can be configured to reject requests with excessively large headers or chunks before they reach the backend Perl application. Additionally, implementing rate limiting and connection timeouts at the network perimeter can help detect and terminate abnormal traffic patterns associated with this type of resource exhaustion attack. Regular auditing of web server configurations against industry standards for input validation is essential to prevent similar flaws from being introduced in future updates or custom implementations.