CVE-2026-105242: Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache lo

This month

MEDIUM 5.3REMOTEWATCHLISTUPGRADE

CVE-2026-105242 is a medium-severity flaw (CVSS 5.3) affecting log4net. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. Reading request parameters triggers ASP.NET request validation, so a request carrying content such as markup made the layout throw and the appender discarded the whole event. A sender could suppress the log record of their own request. Only applications on ASP.NET for .NET Framework whose layout uses %aspnet-request are affected.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 43%)
CISA exploited list	No
Weakness	CWE-755
Published	2026-10-06
Last modified	2026-10-09

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-09 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-06 20:17 UTCPublished CVE record published
2026-10-09 15:28 UTCUpdated Record last modified

apache log4net UPGRADE

Affected: >= 1.2.11 and < 3.5.0

Fixed in: 3.5.0

Safe to downgrade to: a release before 1.2.11

1. Check installed version

apt-cache policy log4net || rpm -q log4net || log4net --version

2. UPGRADE to 3.5.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade log4net

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade log4net

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.2.11 (Debian / Ubuntu)

apt-cache madison log4net sudo apt install log4net=<VERSION_BEFORE_1.2.11> sudo apt-mark hold log4net

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list log4net sudo dnf downgrade log4net-<VERSION_BEFORE_1.2.11> sudo dnf versionlock add log4net

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-105242?

log4net: upgrade to 3.5.0. Exact commands for each OS are on this page.

Is CVE-2026-105242 being exploited?

CVE-2026-105242 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-105242 affect?

CVE-2026-105242 affects log4net. Severity is medium (CVSS 5.3). Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. Reading request parameters triggers ASP.NET request validation, so a request carrying content such as markup made the layo

How urgent is CVE-2026-105242?

Priority 43/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

.NET vulnerabilities

Related CVEs

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References

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