Shamir backup recovery accepts a share at x = 0, so a supplied share can substitute the recovered private key

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

`KeyShares::from_backup_format` (the Shamir backup share reader, public since 0.2.0, the crate's first release) accepted a share whose x coordinate is 0, and `KeyShares::recover_private_key` interpolates the shares at x = 0 to recover the key. At an x of 0 the interpolation answers that share's y value alone, so an attacker who supplies one share in that form — with the share's integrity tag ground to match the honest set's — chooses the recovered key outright. The non-canonical zero x = p works the same way, and a repeated x past the threshold window also passed. An application that recovers a Shamir backup from shares it did not produce — a custodian's medium, a share pasted by hand, a set restored from another writer — could be handed the attacker's key as the recovered one. A set the crate's own writer produces never carries such a share; the door is the reader. 0.8.7 refuses such a set before interpolating (the 0.9 line's next prerelease carries the same refusal). Where…

Published by the source

12 Nov 2026, 12:00 UTC

Last modified by the source

12 Nov 2026, 08:00 UTC

Source last checked

13 Nov 2026, 06:40 UTC

1. Revision 1 · created · 13 Nov 2026

   Published from osv record RUSTSEC-2026-0501

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# Patch Next advisory brief: GHSA-cwxv-4866-5gq2

Advisory: Shamir backup recovery accepts a share at x = 0, so a supplied share can substitute the recovered private key
IDs: GHSA-cwxv-4866-5gq2
Record: https://patchnext.com/advisories/rustsec-2026-0501 (revision 1, source checked 13 Nov 2026, 06:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: bsv-rs 0.9.0-beta.7.0, 0.8.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io bsv-rs: affected >= 0.0.0-0, < 0.8.7; >= 0.9.0-beta.1, < 0.9.0-beta.7.0; fixed in 0.9.0-beta.7.0, 0.8.7

## Suggested inspection (read-only)
- crates.io bsv-rs: 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 bsv-rs.
- 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-2026-0501 (OSV record RUSTSEC-2026-0501 lists affected ranges: crates.io bsv-rs >=0.0.0-0 =0.9.0-beta.1 <0.9.0-beta.7.0 (fixed))

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