Junrar: RarVM VM_JMP maxOpCount bypass causes infinite CPU loop during RAR4 extraction

Why it is Amber

• CVSS 7.5 high
• Remotely exploitable without logging in
• On your watchlist: Maven

Affected packages

References

• https://github.com/advisories/GHSA-h9h9-2rmf-rvhp
• https://github.com/junrar/junrar/security/advisories/GHSA-h9h9-2rmf-rvhp
• https://github.com/junrar/junrar/commit/687a09c42f46066447faa9179ee11314ad6d9afb
• https://github.com/junrar/junrar/releases/tag/v7.6.1
• https://github.com/advisories/GHSA-h9h9-2rmf-rvhp

Original description

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.