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GHSA-G956-PH29-3VQ5

Vulnerability from github – Published: 2026-10-06 21:31 – Updated: 2026-10-06 21:32

Details

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-105244"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-116"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T20:17:16Z",
    "severity": "MODERATE"
  },
  "details": "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": "GHSA-g956-ph29-3vq5",
  "modified": "2026-10-06T21:32:00Z",
  "published": "2026-10-06T21:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-105244"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/logging-log4net/pull/315"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6"
    }
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  "schema_version": "1.4.0",
  "severity": [
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      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

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

Vulnerability from cvelistv5 – Published: 2026-10-06 19:52 – Updated: 2026-10-07 06:12

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

apache mitre root Scorecard

References

4 references

URL	Tags
https://github.com/apache/logging-log4net/pull/315	patch
https://github.com/apache/logging-log4net/commit/…	patch
https://lists.apache.org/thread.html/q7649hhdodth…	vendor-advisory
http://www.openwall.com/lists/oss-security/2026/1…

Impacted products

2 products

Vendor	Product	Version
Apache Software Foundation	Apache log4net	Affected: 1.2.12 , < 3.5.0 (semver)
Apache Software Foundation	Apache log4net	Affected: 56a2e146e21ff4737e1ff3ec308810e667873947 , < 77717061b20d4346b6c0ce6b54643d85fb348bc7 (git)

Credits

The Apache Software Foundation Claude Security Jan Friedrich

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.
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GHSA-G956-PH29-3VQ5

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

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