Unbounded memory allocation in evtx parsing a .wevtcache file

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Affected versions of `evtx` did not bound a per-entry payload length read from a `.wevtcache` file before allocating a buffer sized from it, allowing a tiny crafted file to force a multi-gigabyte allocation and abort the process (out-of-memory denial of service, CWE-400).

Details In `WevtCacheReader::next_entry` (`src/wevt_templates/wevtcache.rs`), the per-entry payload length is read as a `u64` straight from the file and used to size a zeroing buffer before any data is read: ```rust let len = usize::try_from(len_u64)?; // u64 taken directly from the entry header let mut buf = vec![0u8; len]; // unbounded allocation, sized from the file reader.read_exact(&mut buf)?; // only fails AFTER the allocation ``` The only check on `len` is that it fits in `usize`; there is no check that it fits within the bytes remaining in the file. An entry header declaring a ~4 GiB length therefore makes the crate request a ~4 GiB allocation from a file of only ~25 bytes. The sink is reachable…

Published by the source

1 Nov 2026, 12:00 UTC

Last modified by the source

2 Nov 2026, 11:00 UTC

Source last checked

3 Nov 2026, 06:10 UTC

1. Revision 1 · created · 3 Nov 2026

   Published from osv record RUSTSEC-2026-0431

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# Patch Next advisory brief: rustsec-2026-0431

Advisory: Unbounded memory allocation in `evtx` parsing a `.wevtcache` file
IDs: rustsec-2026-0431
Record: https://patchnext.com/advisories/rustsec-2026-0431 (revision 1, source checked 3 Nov 2026, 06:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: evtx 0.15.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io evtx: affected >= 0.11.0, < 0.15.1; fixed in 0.15.1

## Suggested inspection (read-only)
- crates.io evtx: 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 evtx.
- 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://osv.dev/vulnerability/RUSTSEC-2026-0431 (OSV record RUSTSEC-2026-0431 lists affected ranges: crates.io evtx >=0.11.0 <0.15.1 (fixed))

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