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🛡️ CVE-2025-64702 — quic-go

🟡 CVSS 5.3 — Medium ✅ No Known Exploit CWE-770 NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

quic-go HTTP/3 QPACK Header Expansion DoS

Summary

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 header field section (many unique header names and/or large values). The implementation builds an http.Header (used on the http.Request and http.Response, respectively), while only enforcing limits on the size of the (QPACK-compressed) HEADERS frame, but not on the decoded header, leading to memory exhaustion.

Impact

A misbehaving or malicious peer can cause a denial-of-service (DoS) attack on quic-go's HTTP/3 servers or clients by triggering excessive memory allocation, potentially leading to crashes or exhaustion. It affects both servers and clients due to symmetric header construction.

Details

In HTTP/3, headers are compressed using QPACK (RFC 9204). quic-go's HTTP/3 server (and client) decodes the QPACK-encoded HEADERS frame into header fields, then constructs an http.Request (or response).

http3.Server.MaxHeaderBytes and http3.Transport.MaxResponseHeaderBytes, respectively, limit encoded HEADERS frame size (default: 1 MB server, 10 MB client), but not decoded size. A maliciously crafted HEADERS frame can expand to ~50x the encoded size using QPACK static table entries with long names / values.

RFC 9114 requires enforcing decoded field section size limits via SETTINGS, which quic-go did not do.

The Fix

quic-go now enforces RFC 9114 decoded field section size limits, sending SETTINGS_MAX_FIELD_SECTION_SIZE and using incremental QPACK decoding to check the header size after each entry, aborting early on violations with HTTP 431 (on the server side) and stream reset (on the client side).

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: Low — limited, and the attacker does not choose what is affected.

Weakness class

CVE-2025-64702 is classified as CWE-770: Allocation of Resources Without Limits. Resources are allocated on request with no cap, so a client can exhaust them.

Affected software

CVE-2025-64702 is recorded against 2 packages.

  • github.com/quic-go/quic-go
  • quic-go (fixed in 0.57.0)

Timeline and source

Published on 11 December 2025 and last revised on 4 February 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)

Other advisories for this package

github.com/quic-go/quic-go has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-770: Allocation of Resources Without Limits) in other software:

CVE-2025-64702 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Medium
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE CWE-770
Public Exploit ✅ No
Source NVD
Published 2025-12-11
Updated 2026-08-20
Modified 2026-02-04

Affected Packages

Software From version Fixed in
github.com/quic-go/quic-go — —
quic-go — 0.57.0

Similar Threats

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