CVE-2026-40898: quic-go is an implementation of the QUIC protocol in Go

Q: How do I fix CVE-2026-40898?

quic-go: upgrade to 0.59.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-40898 being exploited?

CVE-2026-40898 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-2026-40898 affect?

CVE-2026-40898 affects quic-go. Severity is medium (CVSS 5.3). quic-go is an implementation of the QUIC protocol in Go. Prior to version 0.59.1, an attacker can cause excessive memory allocation in quic-go's HTTP/3 client and server implementations by sending a QPACK-encoded HEADERS frame that decodes

Q: How urgent is CVE-2026-40898?

Priority 32/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-40898 is a medium-severity flaw (CVSS 5.3) affecting quic-go. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

quic-go is an implementation of the QUIC protocol in Go. Prior to version 0.59.1, an attacker can cause excessive memory allocation in quic-go's HTTP/3 client and server implementations by sending a QPACK-encoded HEADERS frame that decodes into a large trailer field section with many unique field names and/or large values. The implementation builds an `http.Header` for the corresponding `http.Request` or `http.Response`, while only enforcing limi

Why this priority

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	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-06-04
Last modified	2026-07-22

Publisher (CNA): GitHub, Inc. · Vendor: quic-go project

Last updated 2026-07-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-04 19:16 UTCPublished CVE record published
2026-07-22 20:10 UTCUpdated Record last modified

quic-go project quic-go UPGRADE

Affected: < 0.59.1

Fixed in: 0.59.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy quic-go || rpm -q quic-go || quic-go --version

2. UPGRADE to 0.59.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade quic-go

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade quic-go

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-2026-40898?

quic-go: upgrade to 0.59.1. Exact commands for each OS are on this page.

Is CVE-2026-40898 being exploited?

CVE-2026-40898 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-2026-40898 affect?

CVE-2026-40898 affects quic-go. Severity is medium (CVSS 5.3). quic-go is an implementation of the QUIC protocol in Go. Prior to version 0.59.1, an attacker can cause excessive memory allocation in quic-go's HTTP/3 client and server implementations by sending a QPACK-encoded HEADERS frame that decodes

How urgent is CVE-2026-40898?

Priority 32/100. Remotely exploitable, no login, no user action

References

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