CVE-2020-13111: NaviServer 4.99.4 to 4.99.19 allows denial of service due to the nsd/driver.c ChunkedDecode function not prope

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HIGH 7.5REMOTEUPGRADE

CVE-2020-13111 is a high-severity flaw (CVSS 7.5) affecting naviserver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NaviServer 4.99.4 to 4.99.19 allows denial of service due to the nsd/driver.c ChunkedDecode function not properly validating the length of a chunk. A remote attacker can craft a chunked-transfer request that will result in a negative value being passed to memmove via the size parameter, causing the process to crash.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 27%)
CISA exploited list	No
Weakness	CWE-20, CWE-787
Published	2020-05-16
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: naviserver project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-05-16 15:15 UTCPublished CVE record published
2026-06-17 02:52 UTCUpdated Record last modified

naviserver project naviserver UPGRADE

Affected: >= 4.99.4 and <= 4.99.19

Fixed in: newer than 4.99.19

Safe to downgrade to: a release before 4.99.4

1. Check installed version

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

2. UPGRADE to newer than 4.99.19 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade naviserver

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 4.99.4 (Debian / Ubuntu)

apt-cache madison naviserver sudo apt install naviserver=<VERSION_BEFORE_4.99.4> sudo apt-mark hold naviserver

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

dnf --showduplicates list naviserver sudo dnf downgrade naviserver-<VERSION_BEFORE_4.99.4> sudo dnf versionlock add naviserver

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-2020-13111?

naviserver: upgrade to newer than 4.99.19. Exact commands for each OS are on this page.

Is CVE-2020-13111 being exploited?

CVE-2020-13111 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-2020-13111 affect?

CVE-2020-13111 affects naviserver. Severity is high (CVSS 7.5). NaviServer 4.99.4 to 4.99.19 allows denial of service due to the nsd/driver.c ChunkedDecode function not properly validating the length of a chunk. A remote attacker can craft a chunked-transfer request that will result in a negative value

How urgent is CVE-2020-13111?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

References

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