CVE-2026-124317 — libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16

Exploitation evidence

Not listed in the latest downloaded CISA KEV catalog. This does not establish an absence of exploitation.

KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗

Reported products and versions

libexpat / libexpat

Default status: unaffected

affected: 0 to ≤ 2.10.0 (semver)

Fixes and workarounds

No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.

Sources and related reporting

CVE Program record ↗ · Download tracked evidence as JSON

Monitored source mentions

BleepingComputer — Microsoft November 2026 Patch Tuesday fixes 1,235 flaws, Outlook zero-day ↗

Shared CVE identifiers link source mentions; they do not establish that the reports describe the same incident.

Observed change timeline

History begins when Egret first downloads each source. It is not the complete upstream CVE history.

12 Nov 2026, 18:20 Jerusalem · EPSS observation updated

Stored EPSS snapshot at this observation.

{
  "date": "2026-11-12",
  "epss": 0.00249,
  "percentile": 0.16318
}

11 Nov 2026, 12:20 Jerusalem · EPSS observation updated

Stored EPSS snapshot at this observation.

{
  "date": "2026-11-10",
  "epss": 0.00249,
  "percentile": 0.16284
}

11 Nov 2026, 12:20 Jerusalem · CVE Program record changed

Stored CNA snapshot at this observation.

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-124317",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-11-11T04:02:14.991976Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-11-11T04:02:24.741Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:github/libexpat/libexpat",
          "product": "libexpat",
          "repo": "https://github.com/libexpat/libexpat",
          "vendor": "libexpat",
          "versions": [
            {
              "lessThanOrEqual": "2.10.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*",
                  "versionEndIncluding": "2.10.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
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      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Oğuzhan Demirbaş"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Sebastian Pipping"
        }
      ],
      "datePublic": "2026-11-06T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications."
        }
      ],
      "metrics": [
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            "attackRequirements": "PRESENT",
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            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
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            "baseScore": 4.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-126",
              "description": "Buffer Over-read",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-07T14:17:57.180Z",
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      "references": [
        {
          "tags": [
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          ],
          "url": "https://github.com/libexpat/libexpat/pull/1492"
        },
        {
          "tags": [
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          "url": "https://github.com/libexpat/libexpat/blob/a70841d9ffa64ddde29ab824ed6305035ebe4c47/expat/lib/xmltok.c#L1274-L1322"
        },
        {
          "tags": [
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          "url": "https://github.com/libexpat/libexpat"
        },
        {
          "name": "VulnCheck Advisory: libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/libexpat-through-2.10.0-out-of-bounds-read-via-unknown-toutf8-and-unknown-toutf16"
        }
      ],
      "title": "libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16",
      "x_generator": {
        "engine": "vulncheck-endgame"
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  "cveMetadata": {
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    "datePublished": "2026-11-07T14:17:57.180Z",
    "dateReserved": "2026-11-07T12:27:50.865Z",
    "dateUpdated": "2026-11-11T04:02:24.741Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}