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.NET
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CRITICAL severity

XML External Entity attack in log4netGHSA-2cwj-8chv-9pp9

CRITICAL

GHSA-2cwj-8chv-9pp9 is a critical-severity (CVSS 9.8) XML External Entity (XXE) vulnerability in log4net. EPSS puts its 30-day exploitation probability at 17.8% (97th percentile). A fix is available for log4net — see the affected versions and patch details below.

Also known asCVE-2018-1285
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
17.8%probability of exploitation in next 30 days
Moderate Risk0.00%
Lower risk than most CVEs97th percentile — riskier than 97% of all scored CVEsHighest risk
0.96%30.1%59.3%88.5%72.1%17.8%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETlog4net

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Apache log4net versions before 2.0.10 do not disable XML external entities when parsing log4net configuration files. This allows for XXE-based attacks in applications that accept attacker-controlled log4net configuration files.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetlog4netall versions2.0.10dotnet add package log4net --version 2.0.10

Affected Products

7 products · 11 configurations
Application
log4netapache
< 2.0.10
range
OS
fedorafedoraproject
3 versions
303132
Application
manageability software development kitnetapp
all
Application
snapcenternetapp
all
Application
application testing suiteoracle
1 version
13.3.0.1
Application
hospitality opera 5oracle
2 versions
5.55.6

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for log4net, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update log4net to 2.0.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2cwj-8chv-9pp9 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Apache log4net before 2.0.10 does not disable XML external entities when parsing log4net configuration files. This could allow for XXE-based attacks in applications that accept arbitrary configuration files from users.
O3 Security · Impact-Aware SCA

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XML External Entity attack in log4net (Critical 9.8)