libreswan — security advisory
Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.
- Products
- libreswan
- Affected versions
- 4.10-2, 4.10-2+deb12u1, 4.11-1, 4.12-1, 4.12-2, 4.12-3, 4.14-1, 4.14-1.1, 4.15-1, 5.0~rc2-1, 5.0~rc2-2, 5.2-1, 5.2-2, 5.2-2.1, 5.2-2.2, 5.2-2.3, 5.2-2.4, 5.2-2.5
- Fixed versions
- 5.2-2.5
- CVEs
- CVE-2026-50721
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:16 UTC · Revision 2
Source evidence
Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.
osv:DEBIAN-CVE-2026-50721
libreswan
Fixed versions: Not specified
libreswan
Fixed versions: Not specified
libreswan
Fixed versions: 5.2-2.5
Complete source record
{
"id": "c0b9c35260f1534d9e88350112cdac92201d323593e1db221bda0e96e6b4640c",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-50721",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-50721",
"summary": "Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.",
"evidence": "osv:DEBIAN-CVE-2026-50721",
"products": [
{
"name": {
"value": "libreswan",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.10-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.10-2+deb12u1",
"evidence": "/affected/0/versions"
},
{
"value": "4.11-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.12-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.12-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.12-3",
"evidence": "/affected/0/versions"
},
{
"value": "4.14-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.14-1.1",
"evidence": "/affected/0/versions"
},
{
"value": "4.15-1",
"evidence": "/affected/0/versions"
},
{
"value": "5.0~rc2-1",
"evidence": "/affected/0/versions"
},
{
"value": "5.0~rc2-2",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2.1",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2.2",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2.3",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2.4",
"evidence": "/affected/0/versions"
},
{
"value": "5.2-2.5",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "libreswan",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.2-2.2",
"evidence": "/affected/1/versions"
},
{
"value": "5.2-2.3",
"evidence": "/affected/1/versions"
},
{
"value": "5.2-2.4",
"evidence": "/affected/1/versions"
},
{
"value": "5.2-2.5",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "libreswan",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.2-2.5",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "5.2-2.2",
"evidence": "/affected/2/versions"
},
{
"value": "5.2-2.3",
"evidence": "/affected/2/versions"
},
{
"value": "5.2-2.4",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2026-50721",
"aliases": [
"DEBIAN-CVE-2026-50721"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "libreswan",
"purl": "pkg:deb/debian/libreswan?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"4.10-2",
"4.10-2+deb12u1",
"4.11-1",
"4.12-1",
"4.12-2",
"4.12-3",
"4.14-1",
"4.14-1.1",
"4.15-1",
"5.0~rc2-1",
"5.0~rc2-2",
"5.2-1",
"5.2-2",
"5.2-2.1",
"5.2-2.2",
"5.2-2.3",
"5.2-2.4",
"5.2-2.5"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50721.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "libreswan",
"purl": "pkg:deb/debian/libreswan?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"5.2-2.2",
"5.2-2.3",
"5.2-2.4",
"5.2-2.5"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50721.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.2-2.5"
}
]
}
],
"package": {
"name": "libreswan",
"purl": "pkg:deb/debian/libreswan?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"5.2-2.2",
"5.2-2.3",
"5.2-2.4"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50721.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-26T11:47:30.082393022Z",
"provider": "osv",
"upstream": [
"CVE-2026-50721"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-50721"
]
},
"related_cves": [
{
"value": "CVE-2026-50721",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 450759,
"published_at": "2026-07-02T22:16:43.367+00:00"
}