Junrar is an open source Java RAR archive library. Prior to 7.6.1, RarVM.ExecuteCode in src/main/java/com/github/junrar/unpack/vm/RarVM.java can repeatedly execute a VM_JMP instruction whose target is greater than or equal to the prepared program's codeSize. The setIP() function returns success without changing the instruction pointer or decrementing maxOpCount, and the jump handler continues before loop-end accounting, leaving both values unchanged. A crafted RAR4 archive can therefore keep an extraction thread in an infinite CPU loop and exhaust archive-processing worker capacity. The RAR virtual machine does not expose native process execution, so the supported impact is availability loss rather than code execution. This issue is fixed in version 7.6.1.

Affected: Maven: com.github.junrar:junrar

### Summary

Junrar's RAR virtual machine can be forced into a deterministic infinite loop while extracting a crafted RAR4 archive. The `RarVM.ExecuteCode` loop is intended to be bounded by `maxOpCount`, but jump instructions can bypass this limit when `setIP()` is called with a target instruction pointer greater than or equal to `codeSize`.

An unauthenticated attacker who can provide a RAR archive to an application using `Junrar.extract()` can cause the extraction thread to spin forever, consuming CPU and blocking the process. The issue is a denial of service vulnerability, not remote code execution.

### Details

The root cause is in `src/main/java/com/github/junrar/unpack/vm/RarVM.java`.

`setIP()` returns early when the target IP is outside the prepared VM program:

```java private boolean setIP(int ip) { if ((ip) >= codeSize) { return (true); }

if (--maxOpCount <= 0) { return (false); }

IP = ip; return true; } ```

When `ip >= codeSize`, this branch:

- does not update `IP`; - does not decrement `maxOpCount`; - returns `true`, so callers treat it as success.

The `VM_JMP` handler and the other jump-like handlers discard the return value of `setIP()` and immediately `continue` the main VM loop:

```java case VM_JMP: setIP(getValue(false, mem, op1)); continue; ```

Because of the `continue`, execution also skips the loop-end accounting:

```java IP++; --maxOpCount; ```

As a result, a VM program containing a single `VM_JM…