{"id":"CVE-2026-63410","aliases":[],"cve":{"records":[{"id":"CVE-2026-63410","source":"GitHub_M","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-07-16T19:20:28.987Z","published":"2026-10-30T22:48:09.173Z","modified":"2026-11-02T14:50:09.239Z"}],"publishers":[{"name":"GitHub_M","role":"CNA","organizationId":"a0819718-46f1-4df5-94e2-005712e83aaa","modified":"2026-10-30T22:48:09.173Z"},{"name":"CISA-ADP","role":"ADP","organizationId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","modified":"2026-11-02T14:50:09.239Z"}],"references":[{"url":"https://github.com/sgbett/secp256k1-native/security/advisories/GHSA-vp2j-gqfm-r3cf","tags":["x_refsource_CONFIRM"],"source":"GitHub_M"},{"url":"https://github.com/sgbett/secp256k1-native/pull/32","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/sgbett/secp256k1-native/commit/a89bea1617a2d063c6545ad44565dc22098c880e","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/sgbett/secp256k1-native/blob/master/docs/advisories/0001-compiler-reconstructed-ct-branch.md","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/sgbett/secp256k1-native/releases/tag/v0.18.0","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/sgbett/secp256k1-native/security/advisories/GHSA-vp2j-gqfm-r3cf","tags":["exploit"],"source":"CISA-ADP"}],"weaknesses":[{"id":"CWE-208","description":"CWE-208: Observable Timing Discrepancy","source":"GitHub_M"},{"id":"CWE-1255","description":"CWE-1255: Comparison Logic is Vulnerable to Power Side-Channel Attacks","source":"GitHub_M"}],"applicability":[],"prioritization":[{"source":"CISA-ADP","type":"SSVC","role":"CISA Coordinator","timestamp":"2026-11-02T14:49:39.327340Z","decisions":[{"name":"Exploitation","value":"poc"},{"name":"Automatable","value":"no"},{"name":"Technical Impact","value":"partial"}]}]},"title":"secp256k1-native: Compiler-reconstructed secret-dependent branch in native scalar multiplication","titleSource":"GitHub_M","descriptionSource":"GitHub_M","description":"secp256k1-native is a native C secp256k1 implementation for Ruby. In affected native builds, native constant-time scalar multiplication through `Point#mul` or `scalar_multiply_ct` can leak timing information about a secret scalar when compiled by a toolchain that reconstructs branchless selection into a branch. The `Montgomery ladder` uses `uint256_select` with an all-zeros or all-ones mask, but affected GCC builds at `-O2` recover the original condition and emit secret-dependent `je` or `jne` jumps whose timing correlates with scalar bits. This defeats the assumption behind the 0.17.0 `jp_add_internal` infinity-branch fix. A consumer must multiply a secret private key or nonce in a context where an attacker can observe timing; repeated measurements can statistically recover scalar bits. The defect is in the compiled binary, so source review or `ctgrind` on a non-reconstructing toolchain may miss it. GCC 14.3.0, 15.1.0, and 15.2.0 reproduced the branch reconstruction, and `extconf.rb` appends `-O2`. Tested GCC versions through 12.4.0 used bitwise operations and GCC 13.3.0 used constant-time `cmov`; the pure-Ruby path is not affected by this flaw and separately makes no constant-time claim. GCC 16 and clang were untested, and point releases, targets, and flag combinations were not exhaustively bisected. `Earlier pre-0.17.0 versions had different constant-time issues rather than this introduced select idiom.` Version 0.18.0 contains the verified fix. The advisory's broad pre-0.18.0 guidance also covers earlier, different constant-time issues; whether this CVE groups those issues or only the select idiom introduced in 0.17.0 remains unresolved.","score":5.9,"severity":"medium","published":"2026-10-30T22:48:09.173Z","modified":"2026-11-02T14:50:09.239Z","withdrawn":false,"knownExploited":false,"affected":[],"products":[{"vendor":"sgbett","name":"secp256k1-native","platforms":[],"versions":[{"version":">= 0.17.0, < 0.18.0","status":"affected"}],"cpes":[],"source":"GitHub_M","url":"https://www.cve.org/CVERecord?id=CVE-2026-63410"}],"remediation":[],"references":["https://github.com/sgbett/secp256k1-native/security/advisories/GHSA-vp2j-gqfm-r3cf","https://github.com/sgbett/secp256k1-native/pull/32","https://github.com/sgbett/secp256k1-native/commit/a89bea1617a2d063c6545ad44565dc22098c880e","https://github.com/sgbett/secp256k1-native/blob/master/docs/advisories/0001-compiler-reconstructed-ct-branch.md","https://github.com/sgbett/secp256k1-native/releases/tag/v0.18.0"],"sources":[{"name":"CVE","id":"CVE-2026-63410","modified":"2026-11-02T14:50:09.239Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-63410"}],"assessments":[{"source":"GitHub_M","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","score":5.9}],"sourceAffected":[],"observedAt":"2026-11-02T14:55:54.002Z","kev":{"status":"not-listed","checkedAt":"2026-11-15T01:25:32.844Z"},"coverage":[{"source":"NVD","status":"refresh-failed","attemptedAt":"2026-10-31T00:00:56.834Z"},{"source":"GHSA","status":"no-result","checkedAt":"2026-10-31T00:00:40.705Z","attemptedAt":"2026-10-31T00:00:40.705Z"},{"source":"EUVD","status":"available","checkedAt":"2026-10-31T00:00:40.713Z","attemptedAt":"2026-10-31T00:00:40.713Z"},{"source":"EPSS","status":"no-result","checkedAt":"2026-10-31T00:00:40.682Z","attemptedAt":"2026-10-31T00:00:40.682Z"}],"evidence":[{"source":"ENISA EUVD","id":"EUVD-2026-114552","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-114552","modified":"Oct 30, 2026, 10:48:09 PM","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","checkedAt":"2026-10-31T00:00:40.713Z"}],"aiSummary":{"text":"secp256k1-native versions 0.17.0 to less than 0.18.0 may leak timing information about a secret scalar when compiled with certain GCC versions. An attacker with access to timing information can statistically recover scalar bits. The issue is due to compiler-reconstructed secret-dependent branches in native scalar multiplication.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-10-31T00:11:03.309Z","sources":[{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-63410"}]}}