dbcve.org
Quic GoApplication · Quic Go Project

CVE-2026-40898

HIGH · 7.5 CVSS v3.1 Published 2026-06-04
Fix available
A fix is available. Upgrade to 0.59.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 limits on the size of the QPACK-compressed HEADERS frame, not on the decoded field section. This can lead to memory exhaustion. This is very similar to CVE-2025-64702. The difference is that this issue uses HTTP trailers, rather than HTTP headers, as the attack vector. A misbehaving or malicious peer can cause a denial-of-service (DoS) attack against quic-go's HTTP/3 servers or clients by triggering excessive memory allocation, potentially leading to crashes or resource exhaustion. This affects both servers and clients due to symmetric header construction. Version 0.59.1 enforces RFC 9114 decoded field section size limits for trailers as well. It incrementally decodes QPACK entries and checks the field section size after each entry, aborting the stream if an entry causes the limit to be exceeded.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

quic-go versions prior to 0.59.1 fail to enforce limits on decoded QPACK trailer field sections, only checking the compressed HEADERS frame size. Attackers can send specially crafted QPACK-encoded HEADERS frames with large trailers containing many unique field names or large values, causing excessive memory allocation and memory exhaustion DoS against HTTP/3 clients and servers.

MitigationUpgrade quic-go to version 0.59.1 or later, which enforces RFC 9114 decoded field section size limits for trailers by incrementally decoding QPACK entries and aborting streams that exceed size limits.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Quic GoApplication
Affected:< 0.59.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify quic-go version in use
    Run 'go list -m all | grep quic-go' or inspect your go.mod file for the quic-go module version
    Affected if The version listed is below 0.59.1 (e.g., 0.59.0, 0.58.0, etc.)
  2. Confirm HTTP/3 traffic handling
    Check if your application initializes an HTTP/3 server or client using quic-go's h3 package. Look for usage of h3.Server or h3.Client in your codebase
    Affected if Your application uses h3.Server or h3.Client to handle HTTP/3 connections
  3. Verify trailer processing is enabled
    Review your HTTP handler code to see if http.Response.Header (trailers) are read or processed after receiving HTTP/3 requests. Check for calls to request.Trailer() or reading from response trailers
    Affected if Your handlers read or process HTTP trailers from incoming requests or outgoing responses
  4. Check for size limits on decoded headers
    Inspect your quic-go or h3 configuration for any custom MaxHeaderBytes or field section size limits. In code, search for h3.Transport settings or quic.Config
    Affected if No decoded field section size limits are configured and you rely on the default quic-go behavior (versions prior to 0.59.1 had no such limits for trailers)

You are affected if your installed quic-go version is below 0.59.1 AND your application processes HTTP/3 traffic with trailers, since prior versions did not enforce limits on decoded trailer sizes.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.59.1 or later
Fixed in 0.59.1
Interim mitigation

Upgrade quic-go to version 0.59.1 or later, which enforces RFC 9114 decoded field section size limits for trailers by incrementally decoding QPACK entries and aborting streams that exceed size limits.

Recommended fix High confidence

quic-go v0.59.1

  1. 1. Identify all Go projects that depend on quic-go library
  2. 2. Run `go list -m all` or check go.mod files to find current quic-go version
  3. 3. Update quic-go to version 0.59.1 or later by running `go get github.com/quic-go/quic-go@latest` or `go get github.com/quic-go/[email protected]`
  4. 4. Run `go mod tidy` to update dependencies and verify the upgrade
  5. 5. Rebuild and test the application to ensure compatibility
  6. 6. Redeploy updated services to production

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Quic Go Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-40898 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data