CVE-2026-105244 (GCVE-0-2026-105244)

Vulnerability from cvelistv5 – Published: 2026-10-06 19:52 – Updated: 2026-10-06 19:52
VLAI
Title
Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content
Summary
Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net. Every character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected. This issue affects Apache log4net: from 1.2.12 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version CPE status
Apache Software Foundation Apache log4net Affected: 1.2.12 , < 3.5.0 (semver)
guessed Create a notification for this product.
Apache Software Foundation Apache log4net Affected: 56a2e146e21ff4737e1ff3ec308810e667873947 , < 77717061b20d4346b6c0ce6b54643d85fb348bc7 (git)
guessed Create a notification for this product.
Credits
The Apache Software Foundation Claude Security Jan Friedrich
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://nuget.org/packages",
          "defaultStatus": "unaffected",
          "packageName": "log4net",
          "packageURL": "pkg:nuget/log4net",
          "product": "Apache log4net",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThan": "3.5.0",
              "status": "affected",
              "version": "1.2.12",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://nuget.org/packages",
          "defaultStatus": "unaffected",
          "packageName": "log4net",
          "packageURL": "pkg:nuget/log4net",
          "product": "Apache log4net",
          "repo": "https://gitbox.apache.org/repos/asf/logging-log4net.git",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThan": "77717061b20d4346b6c0ce6b54643d85fb348bc7",
              "status": "affected",
              "version": "56a2e146e21ff4737e1ff3ec308810e667873947",
              "versionType": "git"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "The Apache Software Foundation"
        },
        {
          "lang": "en",
          "type": "tool",
          "value": "Claude Security"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Jan Friedrich"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net.\u003cbr\u003e\u003cbr\u003eEvery character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.\u003cbr\u003e\u003cbr\u003eThis issue affects Apache log4net: from 1.2.12 before 3.5.0.\u003cbr\u003e\u003cbr\u003eUsers are recommended to upgrade to version 3.5.0, which fixes the issue."
            }
          ],
          "value": "Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net.\n\nEvery character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.12 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "text": "moderate"
            },
            "type": "Textual description of severity"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-116",
              "description": "CWE-116 Improper Encoding or Escaping of Output",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-06T19:52:31.116Z",
        "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
        "shortName": "apache"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/apache/logging-log4net/pull/315"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6"
        }
      ],
      "source": {
        "discovery": "INTERNAL"
      },
      "title": "Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content",
      "x_generator": {
        "engine": "Vulnogram 1.0.3"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
    "assignerShortName": "apache",
    "cveId": "CVE-2026-105244",
    "datePublished": "2026-10-06T19:52:31.116Z",
    "dateReserved": "2026-10-04T16:22:18.416Z",
    "dateUpdated": "2026-10-06T19:52:31.116Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://nuget.org/packages",
                "defaultStatus": "unaffected",
                "packageName": "log4net",
                "packageURL": "pkg:nuget/log4net",
                "product": "Apache log4net",
                "vendor": "Apache Software Foundation",
                "versions": [
                  {
                    "lessThan": "3.5.0",
                    "status": "affected",
                    "version": "1.2.12",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "collectionURL": "https://nuget.org/packages",
                "defaultStatus": "unaffected",
                "packageName": "log4net",
                "packageURL": "pkg:nuget/log4net",
                "product": "Apache log4net",
                "repo": "https://gitbox.apache.org/repos/asf/logging-log4net.git",
                "vendor": "Apache Software Foundation",
                "versions": [
                  {
                    "lessThan": "77717061b20d4346b6c0ce6b54643d85fb348bc7",
                    "status": "affected",
                    "version": "56a2e146e21ff4737e1ff3ec308810e667873947",
                    "versionType": "git"
                  }
                ]
              }
            ],
            "source": "security@apache.org"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net.\n\nEvery character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.12 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue."
          }
        ],
        "id": "CVE-2026-105244",
        "lastModified": "2026-10-06T20:17:16.297",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "LOW",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 1.4,
              "source": "security@apache.org",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-06T20:17:16.297",
        "references": [
          {
            "source": "security@apache.org",
            "url": "https://github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7"
          },
          {
            "source": "security@apache.org",
            "url": "https://github.com/apache/logging-log4net/pull/315"
          },
          {
            "source": "security@apache.org",
            "url": "https://lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6"
          }
        ],
        "sourceIdentifier": "security@apache.org",
        "vulnStatus": "Received",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-116"
              }
            ],
            "source": "security@apache.org",
            "type": "Primary"
          }
        ]
      }
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.



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.