CVE-2025-54939: LiteSpeed QUIC (LSQUIC) Library before 4.3.1 has an lsquic_engine_packet_in memory leak.

Q: How do I fix CVE-2025-54939?

litespeed web adc: upgrade to 3.3.1; litespeed web server: upgrade to 6.3.4; lsquic: upgrade to 4.3.1. Exact commands for each OS are on this page.

Q: Is CVE-2025-54939 being exploited?

CVE-2025-54939 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-54939 affect?

CVE-2025-54939 affects litespeed web adc, litespeed web server, lsquic. Severity is medium (CVSS 5.3). LiteSpeed QUIC (LSQUIC) Library before 4.3.1 has an lsquic_engine_packet_in memory leak.

Q: How urgent is CVE-2025-54939?

Priority 43/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADEUPGRADEUPGRADE

CVE-2025-54939 is a medium-severity flaw (CVSS 5.3) affecting litespeed web adc, litespeed web server, lsquic. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

LiteSpeed QUIC (LSQUIC) Library before 4.3.1 has an lsquic_engine_packet_in memory leak.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

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-770, CWE-401
Published	2025-08-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: litespeedtech

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

Am I affected?

Timeline

2025-08-01 06:15 UTCPublished CVE record published
2026-06-17 09:40 UTCUpdated Record last modified

litespeedtech litespeed web adc UPGRADE

Affected: < 3.3.1

Fixed in: 3.3.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy litespeed-web-adc || rpm -q litespeed-web-adc || litespeed-web-adc --version

2. UPGRADE to 3.3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade litespeed-web-adc

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade litespeed-web-adc

Note

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

litespeedtech litespeed web server UPGRADE

Affected: < 6.3.4

Fixed in: 6.3.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy litespeed-web-server || rpm -q litespeed-web-server || litespeed-web-server --version

2. UPGRADE to 6.3.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade litespeed-web-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade litespeed-web-server

Note

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

litespeedtech lsquic UPGRADE

Affected: < 4.3.1

Fixed in: 4.3.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 4.3.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lsquic

Note

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

litespeedtech openlitespeed UPGRADE

Affected: < 1.8.4

Fixed in: 1.8.4

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.8.4 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openlitespeed

Note

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

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-2025-54939?

litespeed web adc: upgrade to 3.3.1; litespeed web server: upgrade to 6.3.4; lsquic: upgrade to 4.3.1. Exact commands for each OS are on this page.

Is CVE-2025-54939 being exploited?

CVE-2025-54939 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-2025-54939 affect?

CVE-2025-54939 affects litespeed web adc, litespeed web server, lsquic. Severity is medium (CVSS 5.3). LiteSpeed QUIC (LSQUIC) Library before 4.3.1 has an lsquic_engine_packet_in memory leak.

How urgent is CVE-2025-54939?

Priority 43/100. Public exploit reference; Remotely exploitable, no login, no user action

References

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