OW2 ASM EUVD-2026-101219

Exploitation requires the target application to pass an attacker-controlled/crafted Java class file into ASM's Analyzer.analyze() using one of the BasicVerifier, SimpleVerifier, or SourceInterpreter implementations; this is the specific feature that drives the unbounded per-instruction Frame allocation and fix-point iteration. It is therefore limited to deployments that perform bytecode analysis or verification on untrusted input (e.g. plugin/class loaders, sandboxes, or security scanners) - ASM used only on trusted, build-time bytecode is not meaningfully exposed. Limiting factors: the victim must actually invoke the analysis path (UI:P), the vector is local rather than remote by default (AV:L), and impact is confined to availability (no data disclosure or modification). Affected versions are 1.4.3 before 9.11.

This is a medium-severity, availability-only denial-of-service flaw whose signals are internally consistent but point to limited urgency. The vendor-supplied CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H) scores 6.8 and reflects the true shape of the bug: no confidentiality or integrity impact, only resource exhaustion (VA:H), and a local/passive vector in which a victim application must process an attacker-supplied class file. No EPSS score, CISA KEV listing, or public proof-of-concept was provided in the input, so there is no positive signal of active or imminent exploitation; status is 'no public exploit identified at time of analysis.' The flaw was reported by VulnCheck and a patch is confirmed available (fixed in 9.11). The main caveat is exposure rather than severity: ASM is an enormously widespread Java library, but the vulnerable path (Analyzer.analyze() via BasicVerifier/SimpleVerifier/SourceInterpreter) is only reachable in applications that run bytecode analysis on untrusted class files, which is a narrow subset of ASM deployments. Net: a legitimate but non-emergency patch priority - real where untrusted bytecode is analyzed, low practical risk for the typical build-time or trusted-input ASM usage. Note the vector is AV:L/UI:P rather than AV:N; if an application accepts class files over the network for analysis, defenders should treat effective reachability as broader than the local label implies and verify their own data flow.

An application or service that uses ASM's tree analysis API to verify or inspect user-submitted Java bytecode (for example a plugin loader, bytecode scanner, or online code sandbox) receives a maliciously crafted class file. When it passes that class through Analyzer.analyze() with BasicVerifier, SimpleVerifier, or SourceInterpreter, the analyzer performs unbounded per-instruction Frame allocation and fix-point iterations, exhausting memory and CPU until the process hangs or crashes. No public exploit code is identified in the provided data, and the attack requires the victim application to actually analyze the attacker's file (UI:P).