smallbitvec: Integer overflow in safe API leads to heap buffer overflow

Exploitation

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

CVSS

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

EPSS

• CVE-2026-44983: 0.15% estimated exploitation activity in the next 30 days; percentile 4.30 (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.

Summary An integer overflow in the internal capacity calculation of smallbitvec can lead to an undersized heap allocation, resulting in a heap buffer overflow through safe APIs only. This allows memory corruption without requiring unsafe code from the caller. Details The issue originates from unchecked arithmetic in the internal helper function responsible for computing the required buffer size: When cap is close to usize::MAX, the addition: can overflow in release builds and wrap around due to Rust’s default wrapping semantics for integer overflow in optimized builds. As a result: - bufferlen(cap) may return a value significantly smaller than required. - The backing storage is allocated with insufficient size. - Internal metadata (logical length/capacity) reflects a much larger size than the actual allocation. Subsequent safe API calls (e.g., set, push, reserve) rely on this corrupted metadata and perform index computations that assume sufficient backing storage. These operations…

Published by the source

9 May 2026, 00:02 UTC

Last modified by the source

8 Jun 2026, 23:35 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-97wc-2hqc-cjgr

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# Patch Next advisory brief: CVE-2026-44983

Advisory: smallbitvec: Integer overflow in safe API leads to heap buffer overflow
IDs: CVE-2026-44983, GHSA-97wc-2hqc-cjgr
Record: https://patchnext.com/advisories/cve-2026-44983 (revision 1, source checked 26 Oct 2026, 15:42 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 response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io smallbitvec: affected >= 1.0.1, <= 2.6.0

## Suggested inspection (read-only)
- crates.io smallbitvec: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on smallbitvec.
- 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-97wc-2hqc-cjgr (GitHub-reviewed advisory GHSA-97wc-2hqc-cjgr lists affected ranges: crates.io smallbitvec >=1.0.1 <=2.6.0)

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