CVE-2026-110591 in ASM
Summary
by MITRE • 10/14/2026
OW2 ASM 1.4.3 before 9.11 contains an excessive resource consumption vulnerability in Analyzer.analyze() that allows attackers to exhaust memory and CPU via crafted class files. Attackers can supply class files analysed through BasicVerifier, SimpleVerifier or SourceInterpreter to trigger unbounded per-instruction Frame allocation and fix point iterations, causing denial of service.
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Analysis
by VulDB Data Team • 10/14/2026
The OW2 ASM library is a widely used Java bytecode manipulation framework that provides tools for analyzing, transforming, and generating Java classes. Version 1.4.3 through the release prior to 9.11 contains a critical vulnerability within its core analysis components, specifically affecting the Analyzer class and related verification mechanisms such as BasicVerifier, SimpleVerifier, and SourceInterpreter. This flaw represents an excessive resource consumption issue that can be exploited by attackers to cause denial of service conditions against systems relying on ASM for bytecode processing tasks.
The technical root of this vulnerability lies in how the library handles frame allocation during the analysis phase. When analyzing Java class files, particularly those processed through verification or interpretation routines, the Analyzer allocates execution frames per instruction. In vulnerable versions, there is no effective bound on these allocations when encountering crafted inputs. Attackers can construct malicious class files designed to trigger unbounded recursion or iterative loops within the bytecode logic. These crafted classes force the ASM engine into fix-point iterations that do not terminate efficiently, leading to continuous memory allocation and CPU cycles being consumed without limit.
This behavior directly impacts system stability by exhausting available heap space and processor resources. Since Java applications often run with limited garbage collection efficiency under high churn conditions, the rapid creation of frame objects can quickly lead to OutOfMemoryError exceptions or severe performance degradation. The vulnerability is particularly dangerous in environments where ASM is used for dynamic class loading, instrumentation, or security scanning purposes, as it allows a single malicious input file to compromise the availability of the entire application server or service hosting the analysis routine.
From an industry standard perspective, this flaw aligns with CWE-400: Uncontrolled Resource Consumption and CWE-755: Improper Handling of Unexpected or Unusual Input Conditions. It also maps to MITRE ATT&CK technique T1496: Resource Hijacking, where adversaries leverage computational resources for denial-of-service rather than data exfiltration or system control. The lack of input validation regarding the complexity and depth of bytecode structures allows external actors to manipulate internal resource limits effectively.
Mitigation strategies primarily involve upgrading to ASM version 9.11 or later, which addresses these allocation bounds and iteration controls. For organizations unable to upgrade immediately, implementing strict size limits on incoming class files can provide a partial defense in depth. Additionally, running bytecode analysis routines within isolated sandboxed environments with memory caps prevents the vulnerability from affecting critical system resources. Security teams should also audit their use of ASM for any custom verifiers or interpreters that might bypass default protections and ensure that all third-party libraries are kept up to date against known resource exhaustion flaws.