rustsec-2024-0344
Vulnerability from osv_rustsec
Timing variability of any kind is problematic when working with potentially secret values such as
elliptic curve scalars, and such issues can potentially leak private keys and other secrets. Such a
problem was recently discovered in curve25519-dalek.
The Scalar29::sub (32-bit) and Scalar52::sub (64-bit) functions contained usage of a mask value
inside a loop where LLVM saw an opportunity to insert a branch instruction (jns on x86) to
conditionally bypass this code section when the mask value is set to zero as can be seen in godbolt:
- 32-bit (see L106): https://godbolt.org/z/zvaWxzvqv
- 64-bit (see L48): https://godbolt.org/z/PczYj7Pda
A similar problem was recently discovered in the Kyber reference implementation:
https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/hqbtIGFKIpU/m/cnE3pbueBgAJ
As discussed on that thread, one portable solution, which is also used in this PR, is to introduce a volatile read as an optimization barrier, which prevents the compiler from optimizing it away.
The fix can be validated in godbolt here:
- 32-bit: https://godbolt.org/z/jc9j7eb8E
- 64-bit: https://godbolt.org/z/x8d46Yfah
The problem was discovered and the solution independently verified by Alexander Wagner alexander.wagner@aisec.fraunhofer.de and Lea Themint lea.thiemt@tum.de using their DATA tool:
{
"affected": [
{
"database_specific": {
"categories": [
"crypto-failure"
],
"cvss": null,
"informational": null
},
"ecosystem_specific": {
"affected_functions": null,
"affects": {
"arch": [],
"functions": [],
"os": []
}
},
"package": {
"ecosystem": "crates.io",
"name": "curve25519-dalek",
"purl": "pkg:cargo/curve25519-dalek"
},
"ranges": [
{
"events": [
{
"introduced": "0.0.0-0"
},
{
"fixed": "4.1.3"
}
],
"type": "SEMVER"
}
],
"versions": []
}
],
"aliases": [
"CVE-2024-58262",
"GHSA-x4gp-pqpj-f43q"
],
"database_specific": {
"license": "CC0-1.0"
},
"details": "Timing variability of any kind is problematic when working with potentially secret values such as\nelliptic curve scalars, and such issues can potentially leak private keys and other secrets. Such a\nproblem was recently discovered in `curve25519-dalek`.\n\nThe `Scalar29::sub` (32-bit) and `Scalar52::sub` (64-bit) functions contained usage of a mask value\ninside a loop where LLVM saw an opportunity to insert a branch instruction (`jns` on x86) to\nconditionally bypass this code section when the mask value is set to zero as can be seen in godbolt:\n\n- 32-bit (see L106): \u003chttps://godbolt.org/z/zvaWxzvqv\u003e\n- 64-bit (see L48): \u003chttps://godbolt.org/z/PczYj7Pda\u003e\n\nA similar problem was recently discovered in the Kyber reference implementation:\n\n\u003chttps://groups.google.com/a/list.nist.gov/g/pqc-forum/c/hqbtIGFKIpU/m/cnE3pbueBgAJ\u003e\n\nAs discussed on that thread, one portable solution, which is also used in this PR, is to introduce a\nvolatile read as an optimization barrier, which prevents the compiler from optimizing it away.\n\nThe fix can be validated in godbolt here:\n\n- 32-bit: \u003chttps://godbolt.org/z/jc9j7eb8E\u003e\n- 64-bit: \u003chttps://godbolt.org/z/x8d46Yfah\u003e\n\nThe problem was discovered and the solution independently verified by \nAlexander Wagner \u003calexander.wagner@aisec.fraunhofer.de\u003e and Lea Themint \u003clea.thiemt@tum.de\u003e using\ntheir DATA tool:\n\n\u003chttps://github.com/Fraunhofer-AISEC/DATA\u003e",
"id": "RUSTSEC-2024-0344",
"modified": "2025-10-28T06:02:18Z",
"published": "2024-06-18T12:00:00Z",
"references": [
{
"type": "PACKAGE",
"url": "https://crates.io/crates/curve25519-dalek"
},
{
"type": "ADVISORY",
"url": "https://rustsec.org/advisories/RUSTSEC-2024-0344.html"
},
{
"type": "WEB",
"url": "https://github.com/dalek-cryptography/curve25519-dalek/pull/659"
}
],
"related": [],
"severity": [],
"summary": "Timing variability in `curve25519-dalek`\u0027s `Scalar29::sub`/`Scalar52::sub`"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.