{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-105243 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-105243 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-105243 is a medium-severity denial of service vulnerability in Apache log4net, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-105243 and fix it if it is affected.\n\nWhat it is: CVE-2026-105243 is a medium-severity denial of service vulnerability in Apache log4net, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-105243 in the wild and no public exploit code.\n\nAffected product: Apache log4net. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-105243/ (Markdown: https://insights.sbomify.com/CVE-2026-105243/index.md)","id":"CVE-2026-105243","markdown":"https://insights.sbomify.com/CVE-2026-105243/index.md","name":"CVE-2026-105243","record":{"aliases":["DEBIAN-CVE-2026-105243","GHSA-j8mm-w573-8v6c","UBUNTU-CVE-2026-105243"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Apache log4net","requires_auth":"none","summary":"Attackers can suppress Windows Event Log records by sending oversized messages, causing silent logging failures in applications using Apache log4net.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"apache","cpe":[{"product":"log4net","vendor":"apache"}],"cvss":{"score":5.3,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-778","name":"Insufficient Logging"}],"description":"Insufficient Logging vulnerability in the EventLogAppender of Apache log4net.\n\nLong messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by making it long enough. Only applications on Windows that use EventLogAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":false,"headline":"Apache log4net: Oversize EventLogAppender record silently discarded","id":"CVE-2026-105243","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":0,"n_references":3,"next":{"headline":"Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content","id":"CVE-2026-105244"},"packages":[],"prev":{"headline":"Apache log4net: Request validation failure drops the event in the aspnet-request converter","id":"CVE-2026-105242"},"products":["Apache log4net"],"published":"2026-10-06","related":[{"cvss_score":9.8,"headline":"XML External Entity attack in log4net","id":"CVE-2018-1285","kev_date_added":null,"published":"2020-05-11"},{"cvss_score":6.3,"headline":"Apache Log4net: Silent log event loss in XmlLayout and XmlLayoutSchemaLog4J due to unescaped XML 1.0 forbidden characters","id":"CVE-2026-40021","kev_date_added":null,"published":"2026-04-10"},{"cvss_score":5.3,"headline":"Apache log4net: NUL character truncates EventLogAppender records","id":"CVE-2026-105239","kev_date_added":null,"published":"2026-10-06"},{"cvss_score":5.3,"headline":"Apache log4net: NUL character truncates OutputDebugStringAppender records","id":"CVE-2026-105240","kev_date_added":null,"published":"2026-10-06"},{"cvss_score":5.3,"headline":"Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch","id":"CVE-2026-105241","kev_date_added":null,"published":"2026-10-06"},{"cvss_score":5.3,"headline":"Apache log4net: Request validation failure drops the event in the aspnet-request converter","id":"CVE-2026-105242","kev_date_added":null,"published":"2026-10-06"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-07","vendors":["Apache Software Foundation"]},"summary":"Attackers can suppress Windows Event Log records by sending oversized messages, causing silent logging failures in applications using Apache log4net.","url":"https://insights.sbomify.com/CVE-2026-105243/"}