Vulnerability-Lookup

RLSA-2026:72448 (CVE-2026-66046)

Vulnerability from osv_rocky – Published: 2026-09-29 06:01 – Updated: 2026-09-29 12:14 – Source website

Summary

Important: expat security update

Details

Expat is a C library for parsing XML documents.

Security Fix(es):

expat: Expat: Denial of Service via quadratic complexity in attribute processing (CVE-2026-66046)
expat: Expat: XML Injection via Malformed UTF-16 Input (CVE-2026-93990)

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.

Severity

7.5 (High)


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

Credits

Rocky Enterprise Software Foundation

Red Hat

References

URL

Type

	https://errata.rockylinux.org/RLSA-2026:72448	ADVISORY
	https://bugzilla.redhat.com/show_bug.cgi?id=2517901	REPORT
	https://bugzilla.redhat.com/show_bug.cgi?id=2538967	REPORT
	https://access.redhat.com/errata/RHSA-2026:72448	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Rocky Linux:8",
        "name": "expat",
        "purl": "pkg:rpm/rocky-linux/expat?distro=rocky-linux-8\u0026epoch=0"
      },
      "ranges": [
        {
          "database_specific": {
            "yum_repository": "BaseOS"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0:2.5.0-4.el8_10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "credits": [
    {
      "name": "Rocky Enterprise Software Foundation"
    },
    {
      "name": "Red Hat"
    }
  ],
  "database_specific": {
    "license": "CC-BY-4.0",
    "license_url": "https://creativecommons.org/licenses/by/4.0/",
    "source_advisory": "RHSA-2026:72448"
  },
  "details": "Expat is a C library for parsing XML documents.\n\nSecurity Fix(es):\n\n* expat: Expat: Denial of Service via quadratic complexity in attribute processing (CVE-2026-66046)\n\n* expat: Expat: XML Injection via Malformed UTF-16 Input (CVE-2026-93990)\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.",
  "id": "RLSA-2026:72448",
  "modified": "2026-09-29T12:14:53.596966Z",
  "published": "2026-09-29T06:01:09.341360Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://errata.rockylinux.org/RLSA-2026:72448"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2517901"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2538967"
    },
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/errata/RHSA-2026:72448"
    }
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Important: expat security update",
  "upstream": [
    "CVE-2026-66046",
    "CVE-2026-93990"
  ]
}

CVE-2026-66046 (GCVE-0-2026-66046)

Vulnerability from cvelistv5 – Published: 2026-08-18 14:10 – Updated: 2026-08-21 11:20 X_Open Source

Title

Expat Denial of Service via storeAtts() Quadratic Complexity

Summary

Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

Severity

8.7 (High)


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

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-20 13:48 UTC

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/libexpat/libexpat/pull/1321	issue-tracking
https://www.vulncheck.com/advisories/expat-denial…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
libexpat project	libexpat	Affected: 0 , ≤ 2.8.3 (semver)

Date Public

2026-08-13 00:00

Credits

Fabian Wahle (Hap Security) Sebastian Pipping VulnCheck

Show details on NVD website

JSON

To clipboard

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CVE-2026-93990 (GCVE-0-2026-93990)

Vulnerability from cvelistv5 – Published: 2026-09-19 22:58 – Updated: 2026-09-28 16:11

Title

Expat before 2.8.5 Malformed UTF-16 Acceptance via Unchecked Surrogate

Summary

Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following code unit, causing Expat to pass unpaired surrogates to applications built with XML_UNICODE and to silently replace input characters in other builds.

Severity

8.7 (High)


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

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-21 15:10 UTC

CWE

CWE-176 - Improper Handling of Unicode Encoding

Assigner

VulnCheck mitre root

References

6 references

URL	Tags
https://github.com/libexpat/libexpat/pull/1282	issue-trackingpatch
https://github.com/libexpat/libexpat/commit/ff6e1…	patch
https://github.com/libexpat/libexpat/releases/tag…	release-notes
https://blog.hartwork.org/posts/expat-2-8-5-released/	vendor-advisory
https://github.com/libexpat/libexpat	product
https://www.vulncheck.com/advisories/expat-throug…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
libexpat	libexpat	Affected: 0 , < 2.8.5 (semver) Unaffected: 2.8.5 (semver) cpe:2.3:a:libexpat_project:libexpat::::::::

Date Public

2026-09-18 00:00

Credits

Kartik Kenchi (netliomax25-code)

Show details on NVD website

JSON

To clipboard

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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.

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.

Action not permitted

RLSA-2026:72448 (CVE-2026-66046)

CVE-2026-66046 (GCVE-0-2026-66046)

CVE-2026-93990 (GCVE-0-2026-93990)

Tags

Sightings

Nomenclature

Related by attack behaviour