zlib-rs stack overflow during decompression with malicious input

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

A denial of service vulnerability was found in zlib-rs, triggered by specially constructed input. This input causes a stack overflow, resulting in the process using zlib-rs to crash. Impact Due to the way LLVM handles the zlib-rs codebase, tail calls were not guaranteed. This caused certain input patterns to result in a large number of stack frames being required, quickly resulting in a stack overflow. These are unlikely to occur in practice, but a dedicated attacker can construct malicious input files. After stack overflows were found by @inahga with a fuzzer, we dove into the assembly, and found some cases where the stack grew LLVM wants to centralize the cleanup before the return (many other blocks jump to LBB109311), thereby invalidating a tail call to typedo. We were not able to get rid of this call without introducing one elsewhere: we just don't currently have the power to tell LLVM what we want it to do. So, we switch back to loop+match waiting for changes to rust to make a…

Published by the source

14 Nov 2024, 18:09 UTC

Last modified by the source

4 Dec 2024, 16:22 UTC

Source last checked

26 Oct 2026, 15:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-j3px-q95c-9683

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# Patch Next advisory brief: GHSA-j3px-q95c-9683

Advisory: zlib-rs stack overflow during decompression with malicious input
IDs: GHSA-j3px-q95c-9683
Record: https://patchnext.com/advisories/ghsa-j3px-q95c-9683 (revision 1, source checked 26 Oct 2026, 15:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zlib-rs 0.4.0; libz-rs-sys-cdylib 0.4.0; libz-rs-sys 0.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io zlib-rs: affected <= 0.3.1; fixed in 0.4.0
- crates.io libz-rs-sys-cdylib: affected <= 0.3.1; fixed in 0.4.0
- crates.io libz-rs-sys: affected <= 0.3.1; fixed in 0.4.0

## Suggested inspection (read-only)
- crates.io zlib-rs: check the installed version with your package manager.
- crates.io libz-rs-sys-cdylib: check the installed version with your package manager.
- crates.io libz-rs-sys: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on zlib-rs, libz-rs-sys-cdylib, libz-rs-sys.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-j3px-q95c-9683 (GitHub-reviewed advisory GHSA-j3px-q95c-9683 lists affected ranges: crates.io zlib-rs >=0 =0 =0 <=0.3.1)

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