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RUSTSEC-2026-0312 (GHSA-39MM-4Q6X-3VRX)
Vulnerability from osv_rustsec – Published: 2026-09-24 12:00 – Updated: 2026-09-28 09:30 – Source websiteAn excluded_subtrees iPAddress name constraint with an all-zero mask
(0.0.0.0/0 or ::/0) does not restrict iPAddress SANs in certificates issued
beneath it. The mask check treated an all-zero mask as matching nothing, when a
/0 prefix matches every address of its family, so the exclusion was silently
ignored.
CA/Browser Forum Baseline Requirements §7.1.2.5.2 require exactly these
exclusions on every technically constrained sub-CA that may not issue for IP
addresses. As a result, anyone holding (or having compromised) the key of such
a sub-CA can issue a certificate for an arbitrary IP address, and Validator
with RFC5280Policy and ServerIdentityPolicy accepts it for that address. A
permitted_subtrees dNSName entry on the same issuer does not prevent this,
because iPAddress SANs are a different name form.
All users of Validator with RFC5280Policy are affected when a chain can
contain a name-constrained issuer with an all-zero iPAddress exclusion.
The issue is fixed in x509-validator 0.3.1 (commit da661f8). Users should upgrade to 0.3.1 or later.
{
"affected": [
{
"database_specific": {
"categories": [
"crypto-failure"
],
"cvss": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
"informational": null
},
"ecosystem_specific": {
"affected_functions": null,
"affects": {
"arch": [],
"functions": [],
"os": []
}
},
"package": {
"ecosystem": "crates.io",
"name": "x509-validator",
"purl": "pkg:cargo/x509-validator"
},
"ranges": [
{
"events": [
{
"introduced": "0.0.0-0"
},
{
"fixed": "0.3.1"
}
],
"type": "SEMVER"
}
],
"versions": []
}
],
"aliases": [
"GHSA-39mm-4q6x-3vrx"
],
"database_specific": {
"license": "CC0-1.0"
},
"details": "An `excluded_subtrees` iPAddress name constraint with an all-zero mask\n(`0.0.0.0/0` or `::/0`) does not restrict iPAddress SANs in certificates issued\nbeneath it. The mask check treated an all-zero mask as matching nothing, when a\n`/0` prefix matches every address of its family, so the exclusion was silently\nignored.\n\nCA/Browser Forum Baseline Requirements \u00a77.1.2.5.2 require exactly these\nexclusions on every technically constrained sub-CA that may not issue for IP\naddresses. As a result, anyone holding (or having compromised) the key of such\na sub-CA can issue a certificate for an arbitrary IP address, and `Validator`\nwith `RFC5280Policy` and `ServerIdentityPolicy` accepts it for that address. A\n`permitted_subtrees` dNSName entry on the same issuer does not prevent this,\nbecause iPAddress SANs are a different name form.\n\nAll users of `Validator` with `RFC5280Policy` are affected when a chain can\ncontain a name-constrained issuer with an all-zero iPAddress exclusion.\n\nThe issue is fixed in x509-validator 0.3.1 (commit\n[da661f8](https://github.com/namecare/x509-validator/commit/da661f8ecee820e05d089a76ecb654ff52a2c987)).\nUsers should upgrade to 0.3.1 or later.",
"id": "RUSTSEC-2026-0312",
"modified": "2026-09-28T09:30:11Z",
"published": "2026-09-24T12:00:00Z",
"references": [
{
"type": "PACKAGE",
"url": "https://crates.io/crates/x509-validator"
},
{
"type": "ADVISORY",
"url": "https://rustsec.org/advisories/RUSTSEC-2026-0312.html"
},
{
"type": "WEB",
"url": "https://github.com/namecare/x509-validator/commit/da661f8ecee820e05d089a76ecb654ff52a2c987"
}
],
"related": [],
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "Excluded iPAddress name constraints with an all-zero mask are not applied"
}