Use after free in Rocket

Exploitation

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

CVSS

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

EPSS

• CVE-2021-29935: 1.03% estimated exploitation activity in the next 30 days; percentile 63.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Affected versions of this crate transmuted a &str to a &'static str before pushing it into a StackVec, this value was then popped later in the same function. This was assumed to be safe because the reference would be valid while the method's stack was active. In between the push and the pop, however, a function f was called that could invoke a user provided function. If the user provided panicked, then the assumption used by the function was no longer true and the transmute to &'static would create an illegal static reference to the string. This could result in a freed string being used during (such as in a Drop implementation) or after (e.g through catchunwind) the panic unwinding. This flaw was corrected in commit e325e2f by using a guard object to ensure that the &'static str was dropped inside the function.

Published by the source

25 Aug 2021, 20:54 UTC

Last modified by the source

13 Jun 2023, 20:47 UTC

Source last checked

26 Oct 2026, 15:34 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vcw4-8ph6-7vw8

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# Patch Next advisory brief: CVE-2021-29935

Advisory: Use after free in Rocket
IDs: CVE-2021-29935, GHSA-vcw4-8ph6-7vw8
Record: https://patchnext.com/advisories/cve-2021-29935 (revision 1, source checked 26 Oct 2026, 15:34 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rocket 0.4.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io rocket: affected < 0.4.7; fixed in 0.4.7

## Suggested inspection (read-only)
- crates.io rocket: 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 rocket.
- 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-vcw4-8ph6-7vw8 (GitHub-reviewed advisory GHSA-vcw4-8ph6-7vw8 lists affected ranges: crates.io rocket >=0 <0.4.7)

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