{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63410","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-07-16T19:20:28.987Z","datePublished":"2026-10-30T22:48:09.173Z","dateUpdated":"2026-10-30T22:48:09.173Z"},"containers":{"cna":{"title":"secp256k1-native: Compiler-reconstructed secret-dependent branch in native scalar multiplication","problemTypes":[{"descriptions":[{"cweId":"CWE-208","lang":"en","description":"CWE-208: Observable Timing Discrepancy","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1255","lang":"en","description":"CWE-1255: Comparison Logic is Vulnerable to Power Side-Channel Attacks","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.9,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/sgbett/secp256k1-native/security/advisories/GHSA-vp2j-gqfm-r3cf","tags":["x_refsource_CONFIRM"],"url":"https://github.com/sgbett/secp256k1-native/security/advisories/GHSA-vp2j-gqfm-r3cf"},{"name":"https://github.com/sgbett/secp256k1-native/pull/32","tags":["x_refsource_MISC"],"url":"https://github.com/sgbett/secp256k1-native/pull/32"},{"name":"https://github.com/sgbett/secp256k1-native/commit/a89bea1617a2d063c6545ad44565dc22098c880e","tags":["x_refsource_MISC"],"url":"https://github.com/sgbett/secp256k1-native/commit/a89bea1617a2d063c6545ad44565dc22098c880e"},{"name":"https://github.com/sgbett/secp256k1-native/blob/master/docs/advisories/0001-compiler-reconstructed-ct-branch.md","tags":["x_refsource_MISC"],"url":"https://github.com/sgbett/secp256k1-native/blob/master/docs/advisories/0001-compiler-reconstructed-ct-branch.md"},{"name":"https://github.com/sgbett/secp256k1-native/releases/tag/v0.18.0","tags":["x_refsource_MISC"],"url":"https://github.com/sgbett/secp256k1-native/releases/tag/v0.18.0"}],"affected":[{"vendor":"sgbett","product":"secp256k1-native","versions":[{"version":">= 0.17.0, < 0.18.0","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-10-30T22:48:09.173Z"},"descriptions":[{"lang":"en","value":"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."}],"source":{"advisory":"GHSA-vp2j-gqfm-r3cf","discovery":"UNKNOWN"}}}}