{"id":"RUSTSEC-2026-0344","title":"Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)","summary":"Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","vendor":"ruzstd","product":"ruzstd","ecosystem":"rust","affected":["ruzstd >= 0.0.0-0, < 0.9.1"],"patched":["ruzstd 0.9.1"],"published":"2026-10-11","updated":"2026-10-13","sourceUpdated":"2026-10-13T10:45:04.080993335Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/RUSTSEC-2026-0344","references":[{"url":"https://crates.io/crates/ruzstd"},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0344.html"},{"url":"https://github.com/KillingSpark/zstd-rs/commit/d3907c960ca4a1aa44cc38340137c5679dd98f5a"}],"tags":["osv","rust"],"ingestedAt":"2026-10-13T11:45:30.201Z","slug":"RUSTSEC-2026-0344","body":"## Overview\n\nA crafted `.zst` input under 128 KB can force `ruzstd` to allocate several gigabytes at once, crashing the process with an out-of-memory condition. Since `ruzstd` is a decoder for untrusted input, a single small file is enough to take down anything decoding it.\n\nThe compressed size of a block was capped at 128 KB, but a compressed block's **decompressed** size was never checked against `Block_Maximum_Size = min(Window_Size, 128 KiB)` (RFC 8878). In `execute_sequences` the output was built with no running bound and no flush between blocks, so one block could expand to gigabytes — bypassing both the configured window-size limit and the block-by-block streaming that would otherwise release memory. (A related `u32` counter overflow on such a block caused an additional panic.)\n\nThis is a denial of service only; memory access stays in bounds (no corruption, no RCE).\n\n`ruzstd` is also built as a dependency of the Rust standard library via `rustc-dep-of-std`; in the toolchain it is used only to load zstd-compressed debug symbols, so the toolchain-side impact is limited.\n\n**Fixed in 0.9.1** (commit `d3907c9`), which enforces the per-block output bound. Upgrade to `ruzstd >= 0.9.1`.\n\n## Affected packages\n\n- `ruzstd >= 0.0.0-0, < 0.9.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `ruzstd 0.9.1`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}