Vulnerability-Lookup

alsa-2026:55855

Vulnerability from osv_almalinux

Published

2026-08-17 00:00

Modified

2026-08-18 11:15

Summary

Important: libssh security update

Details

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

libssh: libssh: information disclosure via short GSSAPI Curve25519 public key (CVE-2026-59842)
libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843)
libssh: libssh: denial of service via oversized SFTP read length (CVE-2026-59844)
libssh: libssh: denial of service via unchecked ProxyCommand fork() failure (CVE-2026-59845)
libssh: libssh: information disclosure via ProxyCommand %r username expansion (CVE-2026-59846)
libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification (CVE-2026-59847)
libssh: libssh: denial of service via SFTP responses with unknown request IDs (CVE-2026-59848)
libssh: libssh: denial of service via automatic certificate authentication loop (CVE-2026-59849)
libssh: libssh: use-after-free via data callbacks on closed channels (CVE-2026-59850)
libssh: libssh: authentication bypass via missing GSSAPI principal check (CVE-2026-59851)
libssh: libssh: stack buffer overflow in SFTP server longname construction (CVE-2026-15370)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

References

URL

Type

	https://access.redhat.com/errata/RHSA-2026:55855	ADVISORY
	https://access.redhat.com/security/cve/CVE-2026-15370	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59842	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59843	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59844	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59845	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59846	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59847	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59848	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59849	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59850	REPORT
	https://access.redhat.com/security/cve/CVE-2026-59851	REPORT
	https://bugzilla.redhat.com/2498168	REPORT
	https://bugzilla.redhat.com/2498176	REPORT
	https://bugzilla.redhat.com/2498177	REPORT
	https://bugzilla.redhat.com/2498178	REPORT
	https://bugzilla.redhat.com/2498179	REPORT
	https://bugzilla.redhat.com/2498180	REPORT
	https://bugzilla.redhat.com/2498181	REPORT
	https://bugzilla.redhat.com/2498182	REPORT
	https://bugzilla.redhat.com/2498183	REPORT
	https://bugzilla.redhat.com/2498184	REPORT
	https://bugzilla.redhat.com/2499049	REPORT
	https://errata.almalinux.org/10/ALSA-2026-55855.html	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "libssh"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.12.0-3.el10_2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "libssh-config"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.12.0-3.el10_2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "libssh-devel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.12.0-3.el10_2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.  \n\nSecurity Fix(es):  \n\n  * libssh: libssh: information disclosure via short GSSAPI Curve25519 public key (CVE-2026-59842)\n  * libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843)\n  * libssh: libssh: denial of service via oversized SFTP read length (CVE-2026-59844)\n  * libssh: libssh: denial of service via unchecked ProxyCommand fork() failure (CVE-2026-59845)\n  * libssh: libssh: information disclosure via ProxyCommand %r username expansion (CVE-2026-59846)\n  * libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification (CVE-2026-59847)\n  * libssh: libssh: denial of service via SFTP responses with unknown request IDs (CVE-2026-59848)\n  * libssh: libssh: denial of service via automatic certificate authentication loop (CVE-2026-59849)\n  * libssh: libssh: use-after-free via data callbacks on closed channels (CVE-2026-59850)\n  * libssh: libssh: authentication bypass via missing GSSAPI principal check (CVE-2026-59851)\n  * libssh: libssh: stack buffer overflow in SFTP server longname construction (CVE-2026-15370)\n\n\nFor more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.\n",
  "id": "ALSA-2026:55855",
  "modified": "2026-08-18T11:15:41Z",
  "published": "2026-08-17T00:00:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/errata/RHSA-2026:55855"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-15370"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59842"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59843"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59844"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59845"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59846"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59847"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59848"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59849"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59850"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-59851"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498168"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498176"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498177"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498178"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498179"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498180"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498181"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498182"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498183"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2498184"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2499049"
    },
    {
      "type": "ADVISORY",
      "url": "https://errata.almalinux.org/10/ALSA-2026-55855.html"
    }
  ],
  "related": [
    "CVE-2026-59842",
    "CVE-2026-59843",
    "CVE-2026-59844",
    "CVE-2026-59845",
    "CVE-2026-59846",
    "CVE-2026-59847",
    "CVE-2026-59848",
    "CVE-2026-59849",
    "CVE-2026-59850",
    "CVE-2026-59851",
    "CVE-2026-15370"
  ],
  "summary": "Important: libssh security update"
}

CVE-2026-59851 (GCVE-0-2026-59851)

Vulnerability from cvelistv5 – Published: 2026-07-21 14:20 – Updated: 2026-08-17 21:38

Title

Libssh: libssh: authentication bypass via missing gssapi principal check

Summary

A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users.

Severity

8.8 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-22 18:14 UTC

CWE

CWE-863 - Incorrect Authorization

Assigner

redhat redhat root

References

4 references

URL	Tags
https://access.redhat.com/errata/RHSA-2026:42922	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:55855	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/security/cve/CVE-2026-59851	vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2498184	issue-trackingx_refsource_REDHAT

Impacted products

4 products

Vendor	Product	Version
Red Hat	Red Hat Enterprise Linux 10	Unaffected: 0:0.12.0-3.el10_2 , < * (rpm) cpe:/o:redhat:enterprise_linux:10.2
Red Hat	Red Hat Hardened Images	Unaffected: 0.12.1-4.hum1 , < * (rpm) cpe:/a:redhat:hummingbird:1
Red Hat	Red Hat Enterprise Linux 8	cpe:/o:redhat:enterprise_linux:8
Red Hat	Red Hat Enterprise Linux 9	cpe:/o:redhat:enterprise_linux:9

Date Public

2026-07-21 14:14

Credits

Red Hat would like to thank Aisle Research for reporting this issue.

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-59851",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-22T18:14:50.808102Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-22T18:15:44.264Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:10.2"
          ],
          "defaultStatus": "affected",
          "packageName": "libssh",
          "product": "Red Hat Enterprise Linux 10",
          "vendor": "Red Hat",
          "versions": [
            {
              "lessThan": "*",
              "status": "unaffected",
              "version": "0:0.12.0-3.el10_2",
              "versionType": "rpm"
            }
          ]
        },
        {
          "collectionURL": "https://catalog.redhat.com/software/containers/",
          "cpes": [
            "cpe:/a:redhat:hummingbird:1"
          ],
          "defaultStatus": "affected",
          "packageName": "libssh-main",
          "product": "Red Hat Hardened Images",
          "vendor": "Red Hat",
          "versions": [
            {
              "lessThan": "*",
              "status": "unaffected",
              "version": "0.12.1-4.hum1",
              "versionType": "rpm"
            }
          ]
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:8"
          ],
          "defaultStatus": "unaffected",
          "packageName": "libssh",
          "product": "Red Hat Enterprise Linux 8",
          "vendor": "Red Hat"
        },
        {
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:9"
          ],
          "defaultStatus": "unaffected",
          "packageName": "libssh",
          "product": "Red Hat Enterprise Linux 9",
          "vendor": "Red Hat"
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Red Hat would like to thank Aisle Research for reporting this issue."
        }
      ],
      "datePublic": "2026-07-21T14:14:14.431Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "namespace": "https://access.redhat.com/security/updates/classification/",
              "value": "Important"
            },
            "type": "Red Hat severity rating"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
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              "description": "Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-08-17T21:38:10.967Z",
        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "shortName": "redhat"
      },
      "references": [
        {
          "name": "RHSA-2026:42922",
          "tags": [
            "vendor-advisory",
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            "x_refsource_REDHAT"
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          "url": "https://access.redhat.com/errata/RHSA-2026:55855"
        },
        {
          "tags": [
            "vdb-entry",
            "x_refsource_REDHAT"
          ],
          "url": "https://access.redhat.com/security/cve/CVE-2026-59851"
        },
        {
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          "tags": [
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          "time": "2026-04-29T10:03:47.442Z",
          "value": "Reported to Red Hat."
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          "time": "2026-07-21T14:14:14.431Z",
          "value": "Made public."
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      ],
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      "workarounds": [
        {
          "lang": "en",
          "value": "Disable GSSAPIKeyExchange."
        }
      ],
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      },
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "cveId": "CVE-2026-59851",
    "datePublished": "2026-07-21T14:20:47.001Z",
    "dateReserved": "2026-07-07T15:40:24.561Z",
    "dateUpdated": "2026-08-17T21:38:10.967Z",
    "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.

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.

Action not permitted

alsa-2026:55855

Vulnerability from osv_almalinux

CVE-2026-59851 (GCVE-0-2026-59851)

Tags

Sightings

Nomenclature