Vulnerability-Lookup

ALSA-2026:64787

Vulnerability from osv_almalinux – Published: 2026-09-08 00:00 – Updated: 2026-09-09 07:48 – Source website

Summary

Moderate: xz security update

Details

XZ Utils is an integrated collection of user-space file compression utilities based on the Lempel-Ziv-Markov chain algorithm (LZMA), which performs lossless data compression. The algorithm provides a high compression ratio while keeping the decompression time short.

Security Fix(es):

xz: XZ Utils: Denial of Service via buffer overflow in index decoding (CVE-2026-34743)

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-2026:64787	ADVISORY
	https://access.redhat.com/security/cve/CVE-2026-34743	REPORT
	https://bugzilla.redhat.com/2454589	REPORT
	https://errata.almalinux.org/10/ALSA-2026-64787.html	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "xz"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:5.6.2-4.el10_2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "xz-devel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:5.6.2-4.el10_2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "xz-libs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:5.6.2-4.el10_2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "AlmaLinux:10",
        "name": "xz-lzma-compat"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:5.6.2-4.el10_2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "XZ Utils is an integrated collection of user-space file compression utilities based on the Lempel-Ziv-Markov chain algorithm (LZMA), which performs lossless data compression. The algorithm provides a high compression ratio while keeping the decompression time short.  \n\nSecurity Fix(es):  \n\n  * xz: XZ Utils: Denial of Service via buffer overflow in index decoding (CVE-2026-34743)\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-2026:64787",
  "modified": "2026-09-09T07:48:03Z",
  "published": "2026-09-08T00:00:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/errata/RHSA-2026:64787"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-34743"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2454589"
    },
    {
      "type": "ADVISORY",
      "url": "https://errata.almalinux.org/10/ALSA-2026-64787.html"
    }
  ],
  "related": [
    "CVE-2026-34743"
  ],
  "summary": "Moderate: xz security update"
}

CVE-2026-34743 (GCVE-0-2026-34743)

Vulnerability from cvelistv5 – Published: 2026-04-02 18:36 – Updated: 2026-07-21 22:19

Title

XZ Utils: Buffer overflow in lzma_index_append()

Summary

XZ Utils provide a general-purpose data-compression library plus command-line tools. Prior to version 5.8.3, if lzma_index_decoder() was used to decode an Index that contained no Records, the resulting lzma_index was left in a state where where a subsequent lzma_index_append() would allocate too little memory, and a buffer overflow would occur. This issue has been patched in version 5.8.3.

Severity

1.7 (Low)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-03 12:58 UTC

CWE

CWE-122 - Heap-based Buffer Overflow

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/tukaani-project/xz/security/ad…	x_refsource_CONFIRM
https://github.com/tukaani-project/xz/commit/c8c2…	x_refsource_MISC
https://github.com/tukaani-project/xz/releases/ta…	x_refsource_MISC
http://www.openwall.com/lists/oss-security/2026/0…
https://lists.debian.org/debian-lts-announce/2026…

Impacted products

1 product

Vendor	Product	Version
tukaani-project	xz	Affected: < 5.8.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-07-21T22:19:21.175Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/03/31/13"
          },
          {
            "url": "https://lists.debian.org/debian-lts-announce/2026/07/msg00034.html"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-34743",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-03T12:58:58.398176Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-03T12:59:06.096Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "xz",
          "vendor": "tukaani-project",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 5.8.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "XZ Utils provide a general-purpose data-compression library plus command-line tools. Prior to version 5.8.3, if lzma_index_decoder() was used to decode an Index that contained no Records, the resulting lzma_index was left in a state where where a subsequent lzma_index_append() would allocate too little memory, and a buffer overflow would occur. This issue has been patched in version 5.8.3."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 1.7,
            "baseSeverity": "LOW",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-122",
              "description": "CWE-122: Heap-based Buffer Overflow",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-02T18:36:37.450Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/tukaani-project/xz/security/advisories/GHSA-x872-m794-cxhv",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/tukaani-project/xz/security/advisories/GHSA-x872-m794-cxhv"
        },
        {
          "name": "https://github.com/tukaani-project/xz/commit/c8c22869e780ff57c96b46939c3d79ff99395f87",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/tukaani-project/xz/commit/c8c22869e780ff57c96b46939c3d79ff99395f87"
        },
        {
          "name": "https://github.com/tukaani-project/xz/releases/tag/v5.8.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/tukaani-project/xz/releases/tag/v5.8.3"
        }
      ],
      "source": {
        "advisory": "GHSA-x872-m794-cxhv",
        "discovery": "UNKNOWN"
      },
      "title": "XZ Utils: Buffer overflow in lzma_index_append()"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-34743",
    "datePublished": "2026-04-02T18:36:37.450Z",
    "dateReserved": "2026-03-30T19:17:10.224Z",
    "dateUpdated": "2026-07-21T22:19:21.175Z",
    "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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.