CVE-2026-116134 in HTTP::Body
Summary
by MITRE • 10/28/2026
HTTP::Body versions before 1.23_01 for Perl allow memory exhaustion via an unbounded multipart part header block.
The multipart parser takes everything up to the first blank line after a boundary as the part's header block, with no limit on its size or number of lines. Every line is stored in the part's header hash, so a block of short lines costs about 60 bytes of memory per input byte.
A remote attacker can exhaust worker memory with a single request.
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Analysis
by VulDB Data Team • 10/28/2026
The HTTP::Body module for Perl, prior to version 1.23_01, contains a critical resource exhaustion vulnerability stemming from the lack of bounds checking in its multipart form data parser. This component is responsible for parsing incoming HTTP requests that utilize the multipart/form-data content type, commonly used when clients upload files or submit complex forms containing binary and text data. The specific flaw resides in how the module processes part headers within a multipart body. According to the RFC 2046 standard governing MIME multipart messages, each part begins with header fields followed by a blank line that separates headers from the actual content payload. In vulnerable versions of HTTP::Body, the parser reads all lines following a boundary delimiter until it encounters this first blank line, treating them as part headers without imposing any limit on their size or quantity.
This architectural oversight allows an attacker to craft a malicious multipart request containing an excessively large header block composed of numerous short header fields. Since every line in this unbounded block is stored individually within the module's internal hash structure representing the part's metadata, memory consumption scales linearly with the input length. Specifically, each byte of input data contributes approximately sixty bytes to the total memory footprint due to Perl's overhead for string storage and hash entry management. Consequently, a single request containing thousands or millions of header lines can rapidly consume available worker process memory, leading to severe performance degradation or complete service unavailability through out-of-memory conditions.
From an operational perspective, this vulnerability poses a significant risk to web applications relying on CGI scripts, mod_perl handlers, or any Perl-based HTTP server that utilizes HTTP::Body for request parsing. A remote attacker can exploit this flaw by sending a single, carefully crafted HTTP POST request with a multipart body featuring a massive header section. This action does not require authentication and targets the underlying worker processes handling incoming traffic. The impact is classified as a denial of service against the application infrastructure rather than data exfiltration or code execution, although the resulting instability may indirectly facilitate other attacks by disrupting normal operations or causing crashes that might reveal sensitive stack traces or configuration details depending on server error handling policies.
This vulnerability aligns with CWE-400, which describes Uncontrolled Resource Consumption, specifically manifesting as a resource exhaustion scenario where an attacker forces the application to allocate excessive memory resources. In terms of offensive security frameworks, this exploit technique corresponds to ATT&CK T1498 Network Denial of Service, particularly sub-technique T1498.002 which involves flooding or overwhelming target systems with high volumes of requests designed to consume specific resources like bandwidth or processing power, in this case memory allocation during parsing. The lack of input validation on the structural components of a standard protocol message highlights a failure to implement defense-in-depth principles regarding resource limits for untrusted inputs.
Mitigation strategies primarily involve upgrading HTTP::Body to version 1.23_01 or later, where developers have implemented safeguards against such excessive header sizes. For environments unable to immediately patch the software, temporary mitigations include configuring reverse proxies like Nginx or Apache to enforce strict limits on request body size and potentially limiting the number of headers allowed in a single HTTP transaction. Additionally, implementing rate-limiting at the network perimeter can help mitigate the impact by restricting the frequency of requests from any single source IP address, thereby reducing the likelihood of successful memory exhaustion attacks before they consume critical system resources. Regular security audits focusing on input validation for multipart parsers are recommended to prevent similar issues in other components or future versions of related libraries.