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HIGH severity

quic-go: Panic occurs when queuing undecryptable packets after handshake completionGHSA-47m2-4cr7-mhcw

HIGHFix: quic-go/quic-go#5354

GHSA-47m2-4cr7-mhcw is a high-severity (CVSS 7.5) Reachable Assertion vulnerability in github.com/quic-go/quic-go. A fix is available for github.com/quic-go/quic-go — see the affected versions and patch details below.

Also known asCVE-2025-59530GO-2025-4017
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-47m2-4cr7-mhcw.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk
0.00%0.32%0.64%0.96%0.0%0.4%0.5%0.5%May 26Nov 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐹github.com/quic-go/quic-go🐹github.com/quic-go/quic-go

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A misbehaving or malicious server can trigger an assertion in a quic-go client (and crash the process) by sending a premature HANDSHAKE_DONE frame during the handshake.

Impact

A misbehaving or malicious server can cause a denial-of-service (DoS) attack on the quic-go client by triggering an assertion failure, leading to a process crash. This requires no authentication and can be exploited during the handshake phase. Observed in the wild with certain server implementations (e.g. Solana's Firedancer QUIC).

Affected Versions

  • All versions prior to v0.49.1 (for the 0.49 branch)
  • Versions v0.50.0 to v0.54.0 (inclusive)
  • Fixed in v0.49.1, v0.54.1, and v0.55.0 onward

Users are recommended to upgrade to the latest patched version in their respective maintenance branch or to v0.55.0 or later.

Details

For a regular 1-RTT handshake, QUIC uses three sets of keys to encrypt / decrypt QUIC packets:

  • Initial keys (derived from a static key and the connection ID)
  • Handshake keys (derived from the client's and server's key shares in the TLS handshake)
  • 1-RTT keys (derived when the TLS handshake finishes)

On the client side, Initial keys are discarded when the first Handshake packet is sent. Handshake keys are discarded when the server's HANDSHAKE_DONE frame is received, as specified in section 4.9.2 of RFC 9001. Crucially, Initial keys are always dropped before Handshake keys in a standard handshake.

Due to packet reordering, it is possible to receive a packet with a higher encryption level before the key for that encryption level has been derived. For example, the server's Handshake packets (containing, among others, the TLS certificate) might arrive before the server's Initial packet (which contains the TLS ServerHello). In that case, the client queues the Handshake packets and decrypts them as soon as it has processed the ServerHello and derived Handshake keys.

After completion of the handshake, Initial and Handshake packets are not needed anymore and will be dropped. quic-go implements an assertion that no packets are queued after completion of the handshake.

A misbehaving or malicious server can trigger this assertion, and thereby cause a panic, by sending a HANDSHAKE_DONE frame before actually completing the handshake. In that case, Handshake keys would be dropped before Initial keys.

This can only happen if the server implementation is misbehaving: the server can only complete the handshake after receiving the client's TLS Finished message (which is sent in Handshake packets).

The Fix

quic-go needs to be able to handle misbehaving server implementations, including those that prematurely send a HANDSHAKE_DONE frame. We now discard Initial keys when receiving a HANDSHAKE_DONE frame, thereby correctly handling premature HANDSHAKE_DONE frames. The fix was implemented in https://github.com/quic-go/quic-go/pull/5354.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/quic-go/quic-goall versions0.49.1go get github.com/quic-go/quic-go@v0.49.1
🐹Gogithub.com/quic-go/quic-go≥ 0.50.0&&< 0.54.10.54.1go get github.com/quic-go/quic-go@v0.54.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/quic-go/quic-go, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/quic-go/quic-go to 0.49.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-47m2-4cr7-mhcw is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

The availability risk is limited to applications which includethe quic-go library. Host Red Hat systems are not at risk of availability degradation.

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for GHSA-47m2-4cr7-mhcw (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Ansible Automation Platform 2.4 for RHEL 8receptor-0:1.6.2-1.el8apRHSA-2025:21706
Red Hat Ansible Automation Platform 2.5 for RHEL 8ansible-builder-0:3.1.1-1.el8apRHSA-2025:23069
Red Hat Ansible Automation Platform 2.6 for RHEL 9receptor-0:1.6.2-2.el9apRHSA-2025:21768
Red Hat Advanced Cluster Management for Kubernetes 2.13rhacm2/lighthouse-agent-rhel9:1782924920RHSA-2026:36873
Red Hat Advanced Cluster Management for Kubernetes 2.14rhacm2/lighthouse-agent-rhel9:v0.21-1762794425RHSA-2025:21892
Red Hat Advanced Cluster Management for Kubernetes 2.15rhacm2/lighthouse-agent-rhel9:v0.22-1764857716RHSA-2025:22784
Red Hat Ansible Automation Platform 2.5ansible-automation-platform-25/receptor-rhel8:1.6RHSA-2025:23131
Red Hat Ansible Automation Platform 2.6ansible-automation-platform-26/ee-supported-rhel9:1.0RHSA-2025:21775

Frequently Asked Questions

## Summary A misbehaving or malicious server can trigger an assertion in a quic-go client (and crash the process) by sending a premature HANDSHAKE_DONE frame during the handshake. ## Impact A misbehaving or malicious server can cause a denial-of-service (DoS) attack on the quic-go client by triggering an assertion failure, leading to a process crash. This requires no authentication and can be exploited during the handshake phase. Observed in the wild with certain server implementations (e.g. Solana's Firedancer QUIC). ## Affected Versions - All versions prior to v0.49.1 (for the 0.49 bran
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