CVE-2022-41556: A resource leak in gw_backend.c in lighttpd 1.4.56 through 1.4.66 could lead to a denial of service (connectio

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HIGH 7.5REMOTEUPGRADEMITIGATE

CVE-2022-41556 is a high-severity flaw (CVSS 7.5) affecting lighttpd, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A resource leak in gw_backend.c in lighttpd 1.4.56 through 1.4.66 could lead to a denial of service (connection-slot exhaustion) after a large amount of anomalous TCP behavior by clients. It is related to RDHUP mishandling in certain HTTP/1.1 chunked situations. Use of mod_fastcgi is, for example, affected. This is fixed in 1.4.67.

Why this priority

High severity
EPSS top 10%: very likely to be exploited
Public exploit reference
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	3.8% (top 10%)
CISA exploited list	No
Weakness	CWE-401
Published	2022-10-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · lighttpd

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

Am I affected?

Timeline

2022-10-06 18:17 UTCPublished CVE record published
2026-06-17 05:03 UTCUpdated Record last modified

lighttpd lighttpd UPGRADE

Affected: >= 1.4.56 and < 1.4.67

Fixed in: 1.4.67

Safe to downgrade to: a release before 1.4.56

1. Check installed version

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

2. UPGRADE to 1.4.67 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lighttpd

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 1.4.56 (Debian / Ubuntu)

apt-cache madison lighttpd sudo apt install lighttpd=<VERSION_BEFORE_1.4.56> sudo apt-mark hold lighttpd

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

dnf --showduplicates list lighttpd sudo dnf downgrade lighttpd-<VERSION_BEFORE_1.4.56> sudo dnf versionlock add lighttpd

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.

fedoraproject fedora MITIGATE

Affected: 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 35

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2022-41556?

lighttpd: upgrade to 1.4.67; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-41556 being exploited?

CVE-2022-41556 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-2022-41556 affect?

CVE-2022-41556 affects lighttpd, fedora. Severity is high (CVSS 7.5). A resource leak in gw_backend.c in lighttpd 1.4.56 through 1.4.66 could lead to a denial of service (connection-slot exhaustion) after a large amount of anomalous TCP behavior by clients. It is related to RDHUP mishandling in certain HTTP/1

How urgent is CVE-2022-41556?

Priority 59/100. High severity; EPSS top 10%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

lighttpd vulnerabilities

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References

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