Vulnerability-Lookup

GHSA-93PJ-2PMF-2X7P

Vulnerability from github – Published: 2026-07-03 00:31 – Updated: 2026-07-03 00:31

Details

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.

Severity

8.1 (High)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-50721"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-347"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-02T22:16:43Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-93pj-2pmf-2x7p",
  "modified": "2026-07-03T00:31:52Z",
  "published": "2026-07-03T00:31:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50721"
    },
    {
      "type": "WEB",
      "url": "https://libreswan.org/security/CVE-2026-50721"
    },
    {
      "type": "WEB",
      "url": "https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt"
    },
    {
      "type": "WEB",
      "url": "https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc2313"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-50721 (GCVE-0-2026-50721)

Vulnerability from cvelistv5 – Published: 2026-07-02 21:44 – Updated: 2026-07-02 21:44

Title

IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload

Summary

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

8.1 (High)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE

CWE-347 - Improper Verification of Cryptographic Signature
CWE-617 - Reachable Assertion

Assigner

libreswan

References

4 references

URL	Tags
https://libreswan.org/security/CVE-2026-50721/CVE…	vendor-advisory
https://libreswan.org/security/CVE-2026-50721/	patch
https://libreswan.org/security/CVE-2026-50722/CVE…	related
https://www.rfc-editor.org/rfc/rfc2313	technical-description

Impacted products

1 product

Vendor	Product	Version
The Libreswan Project	libreswan	Affected: 0 , ≤ 5.3 (semver) Unaffected: 5.3.1 (semver)

Credits

Yeonghyeon Choi Duyeong Kim Andrew Cagney (The Libreswan Team)

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/libreswan/libreswan",
          "defaultStatus": "unaffected",
          "packageName": "libreswan",
          "product": "libreswan",
          "programRoutines": [
            {
              "name": "RSA_authenticate_hash_signature_raw_rsa"
            }
          ],
          "repo": "https://github.com/libreswan/libreswan",
          "vendor": "The Libreswan Project",
          "versions": [
            {
              "lessThanOrEqual": "5.3",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.3.1",
              "versionType": "semver"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "Any server or client that accepts RSA-based IKEv1 connections via the default authby=rsasig option is vulnerable to denial of service. Authentication bypass additionally requires the use of RSA keys with weak exponents (e=3). IKEv1 only supports RSA-SHA1 (PKCS#1 Version 1.5) for public key authentication, so the vulnerable code path cannot be disabled without migrating to IKEv2 or switching to PSK."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Yeonghyeon Choi"
        },
        {
          "lang": "en",
          "type": "finder",
          "value": "Duyeong Kim"
        },
        {
          "lang": "en",
          "type": "analyst",
          "value": "Andrew Cagney (The Libreswan Team)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eLibreswan, 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.\u003c/p\u003e"
            }
          ],
          "value": "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."
        }
      ],
      "exploits": [
        {
          "lang": "en",
          "value": "No known exploitation in the wild. The authentication bypass requires the target to use RSA keys with weak exponents (e=3), which have been disallowed by most cryptographic libraries for at least a decade. The denial-of-service attack is exploitable against any IKEv1 configuration using the default authby=rsasig option."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-463",
          "descriptions": [
            {
              "lang": "en",
              "value": "Denial of Service via assertion failure in pluto daemon when processing malformed RSA PKCS#1 v1.5 SIG payloads in IKEv1"
            }
          ]
        },
        {
          "capecId": "CAPEC-473",
          "descriptions": [
            {
              "lang": "en",
              "value": "Authentication bypass via Bleichenbacher-style signature forgery when weak RSA exponents (e.g., e=3) are in use"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "Weak RSA exponent (e=3) in use, enabling Bleichenbacher signature forgery"
            }
          ]
        },
        {
          "other": {
            "content": {
              "description": "Vendor-assessed severity: Medium. Authentication bypass requires weak RSA exponents (e=3) which have been disallowed by most cryptographic libraries for over a decade. DoS is mitigated by automatic daemon restart.",
              "value": "MEDIUM"
            },
            "type": "vendorSeverity"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-347",
              "description": "CWE-347: Improper Verification of Cryptographic Signature",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-617",
              "description": "CWE-617: Reachable Assertion",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-02T21:44:09.423Z",
        "orgId": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
        "shortName": "libreswan"
      },
      "references": [
        {
          "name": "Libreswan Security Advisory CVE-2026-50721",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt"
        },
        {
          "name": "Libreswan CVE-2026-50721 Patches",
          "tags": [
            "patch"
          ],
          "url": "https://libreswan.org/security/CVE-2026-50721/"
        },
        {
          "name": "Related: CVE-2026-50722 (IKEv2 variant)",
          "tags": [
            "related"
          ],
          "url": "https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt"
        },
        {
          "name": "RFC 2313 - PKCS #1: RSA Encryption Version 1.5",
          "tags": [
            "technical-description"
          ],
          "url": "https://www.rfc-editor.org/rfc/rfc2313"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eUpgrade to libreswan 5.3.1 or later. Patches for libreswan 4.15 and 5.3 are available at \u003ca href=\"https://libreswan.org/security/CVE-2026-50721/\"\u003ehttps://libreswan.org/security/CVE-2026-50721/\u003c/a\u003e\u003c/p\u003e"
            }
          ],
          "value": "Upgrade to libreswan 5.3.1 or later. Patches for libreswan 4.15 and 5.3 are available at https://libreswan.org/security/CVE-2026-50721/"
        }
      ],
      "source": {
        "defects": [
          "CVE-2026-50721"
        ],
        "discovery": "EXTERNAL"
      },
      "taxonomyMappings": [
        {
          "taxonomyName": "ATT\u0026CK",
          "taxonomyRelations": [
            {
              "relationshipName": "maps to",
              "relationshipValue": "Application or System Exploitation (DoS)",
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      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-03-24T00:00:00.000Z",
          "value": "Libreswan notified of the issue via security@libreswan.org"
        },
        {
          "lang": "en",
          "time": "2026-06-16T00:00:00.000Z",
          "value": "Advanced notice given to supported customers and distributions"
        },
        {
          "lang": "en",
          "time": "2026-06-24T00:00:00.000Z",
          "value": "Public announcement and release of libreswan 5.3.1"
        }
      ],
      "title": "IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload",
      "workarounds": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eIKEv1 only supports RSA-SHA1 (PKCS#1 Version 1.5) with public key authentication, so there is no way to disable the vulnerable code path within IKEv1. Migrate IKEv1 connections to IKEv2 where \u003ccode\u003eauthby=ecdsa\u003c/code\u003e or \u003ccode\u003eauthby=rsa-sha2\u003c/code\u003e can be configured. For static tunnel configurations (not Remote Access VPN Client groups), authentication can be changed to use PSK via \u003ccode\u003eauthby=secret\u003c/code\u003e after coordination with the remote peer.\u003c/p\u003e"
            }
          ],
          "value": "IKEv1 only supports RSA-SHA1 (PKCS#1 Version 1.5) with public key authentication, so there is no way to disable the vulnerable code path within IKEv1. Migrate IKEv1 connections to IKEv2 where authby=ecdsa or authby=rsa-sha2 can be configured. For static tunnel configurations (not Remote Access VPN Client groups), authentication can be changed to use PSK via authby=secret after coordination with the remote peer."
        }
      ],
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      }
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  "cveMetadata": {
    "assignerOrgId": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
    "assignerShortName": "libreswan",
    "cveId": "CVE-2026-50721",
    "datePublished": "2026-07-02T21:44:09.423Z",
    "dateReserved": "2026-06-05T16:10:05.751Z",
    "dateUpdated": "2026-07-02T21:44:09.423Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-93PJ-2PMF-2X7P

CVE-2026-50721 (GCVE-0-2026-50721)

Tags

Sightings

Nomenclature