Vulnerability-Lookup

UBUNTU-CVE-2026-77205 (CVE-2026-77205)

Vulnerability from osv_ubuntu – Published: 2026-10-13 22:18 – Updated: 2026-10-13 22:18 – Source website

Details

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Severity

3.7 (Low)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-77205	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-77205	REPORT
	https://libreswan.org/security/CVE-2026-14957/CVE…	REPORT
	https://libreswan.org/security/CVE-2026-77205/	REPORT
	https://libreswan.org/security/CVE-2026-77205/CVE…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "3.23-4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@3.23-4?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.20-7build1",
        "3.21-2",
        "3.22-1",
        "3.22-2",
        "3.22-3",
        "3.22-4",
        "3.23-1",
        "3.23-4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "3.29-2build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@3.29-2build1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.29-2",
        "3.29-2build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "3.32-3ubuntu3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@3.32-3ubuntu3?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.32-3ubuntu3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "4.14-1ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@4.14-1ubuntu2?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.11-1ubuntu1",
        "4.12-1ubuntu1",
        "4.14-1ubuntu1",
        "4.14-1ubuntu2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "5.2-2.2ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.10",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@5.2-2.2ubuntu2?arch=source\u0026distro=stonking"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.2-2.2ubuntu2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libreswan",
            "binary_version": "5.2-2.2ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "libreswan",
        "purl": "pkg:deb/ubuntu/libreswan@5.2-2.2ubuntu2?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.2-2.2ubuntu1",
        "5.2-2.2ubuntu2"
      ]
    }
  ],
  "aliases": [],
  "details": "Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.",
  "id": "UBUNTU-CVE-2026-77205",
  "modified": "2026-10-13T22:18:00Z",
  "published": "2026-10-13T22:18:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-77205"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-77205"
    },
    {
      "type": "REPORT",
      "url": "https://libreswan.org/security/CVE-2026-14957/CVE-2026-14957.txt"
    },
    {
      "type": "REPORT",
      "url": "https://libreswan.org/security/CVE-2026-77205/"
    },
    {
      "type": "REPORT",
      "url": "https://libreswan.org/security/CVE-2026-77205/CVE-2026-77205.txt"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-77205"
  ]
}

CVE-2026-77205 (GCVE-0-2026-77205)

Vulnerability from cvelistv5 – Published: 2026-10-13 21:28 – Updated: 2026-10-16 15:31

Title

Denial of Service via sending bogus X.509 certificates

Summary

Severity

3.7 (Low)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-16 15:14 UTC

CWE

CWE-772 - Missing Release of Resource after Effective Lifetime

Assigner

libreswan CNA under the mitre root

CNA scorecard – unranked: 8 records in the last 180 days, 10 needed details

References

3 references

URL	Tags
https://libreswan.org/security/CVE-2026-77205/CVE…	vendor-advisory
https://libreswan.org/security/CVE-2026-77205/	patch
https://libreswan.org/security/CVE-2026-14957/CVE…	related

Impacted products

1 product

Vendor	Product	Version
The Libreswan Project	libreswan	Affected: 5.3 , ≤ 5.3.2 (semver) Unaffected: 5.3.3 (semver)

Credits

Wojciech Tatarski (TuxCare)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-77205",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-16T15:14:28.040688Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-16T15:31:54.457Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/libreswan/libreswan",
          "defaultStatus": "unaffected",
          "packageName": "libreswan",
          "product": "libreswan",
          "programRoutines": [
            {
              "name": "add_decoded_cert"
            }
          ],
          "repo": "https://github.com/libreswan/libreswan",
          "vendor": "The Libreswan Project",
          "versions": [
            {
              "lessThanOrEqual": "5.3.2",
              "status": "affected",
              "version": "5.3",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.3.3",
              "versionType": "semver"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "Only configurations running in FIPS mode are vulnerable. Verify FIPS mode and loaded CA certificates with \u0027sudo ipsec fipsstatus\u0027 and \u0027sudo ipsec listcacerts\u0027."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Wojciech Tatarski (TuxCare)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted."
        }
      ],
      "exploits": [
        {
          "lang": "en",
          "value": "No known exploitation in the wild. An attacker could trick a peer into connecting to them first to learn the serial number, then use that to prevent the peer from connecting to the legitimate server. Exploitation requires FIPS mode to be enabled."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "Denial of service by preventing legitimate peers from connecting through cache poisoning with bogus certificates"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "other": {
            "content": {
              "description": "Vendor-assessed severity: Low. Exploitation requires FIPS mode to be enabled and either guessing or learning certificate serial numbers. Certificate Authorities should use randomized serial numbers per best practice.",
              "value": "LOW"
            },
            "type": "vendorSeverity"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-772",
              "description": "CWE-772: Missing Release of Resource after Effective Lifetime",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-13T21:28:03.390Z",
        "orgId": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
        "shortName": "libreswan"
      },
      "references": [
        {
          "name": "Libreswan Security Advisory CVE-2026-77205",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://libreswan.org/security/CVE-2026-77205/CVE-2026-77205.txt"
        },
        {
          "name": "Libreswan CVE-2026-77205 Patches",
          "tags": [
            "patch"
          ],
          "url": "https://libreswan.org/security/CVE-2026-77205/"
        },
        {
          "name": "Related: CVE-2026-14957 (incorrect fix being corrected)",
          "tags": [
            "related"
          ],
          "url": "https://libreswan.org/security/CVE-2026-14957/CVE-2026-14957.txt"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to libreswan 5.3.3 or later. Patches are available at https://libreswan.org/security/CVE-2026-77205/"
        }
      ],
      "source": {
        "defects": [
          "CVE-2026-77205"
        ],
        "discovery": "EXTERNAL"
      },
      "taxonomyMappings": [
        {
          "taxonomyName": "ATT\u0026CK",
          "taxonomyRelations": [
            {
              "relationshipName": "maps to",
              "relationshipValue": "Application or System Exploitation (DoS)",
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            }
          ],
          "taxonomyVersion": "15.1"
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-07-30T00:00:00.000Z",
          "value": "Libreswan was notified of the issue via security@libreswan.org"
        },
        {
          "lang": "en",
          "time": "2026-09-24T00:00:00.000Z",
          "value": "Advanced notice given to supported customers and distributions"
        },
        {
          "lang": "en",
          "time": "2026-10-05T00:00:00.000Z",
          "value": "Public announcement and release of libreswan 5.3.3"
        }
      ],
      "title": "Denial of Service via sending bogus X.509 certificates",
      "workarounds": [
        {
          "lang": "en",
          "value": "Disabling FIPS mode will prevent this attack vector. If this is not possible, upgrade to a later libreswan version or apply the available patch."
        }
      ],
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
    "assignerShortName": "libreswan",
    "cveId": "CVE-2026-77205",
    "datePublished": "2026-10-13T21:28:03.390Z",
    "dateReserved": "2026-08-20T18:13:09.377Z",
    "dateUpdated": "2026-10-16T15:31:54.457Z",
    "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.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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