How severe is CVE-2026-31812?

No CVSS score has been assigned to CVE-2026-31812 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-31812?

CVE-2026-31812 affects the following packages: quinn-proto (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2026-31812?

Update quinn-proto to 0.11.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-31812 is resolved across your whole dependency graph.

How do I detect CVE-2026-31812 in my crates.io dependencies?

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

How do I mitigate CVE-2026-31812 if there is no patch (or I can't update yet)?

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.

Is CVE-2026-31812 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-31812 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-31812?

CVE-2026-31812 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 44th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-31812?

CVE-2026-31812 is classified as CWE-248 (CWE-248). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-31812 published, and has it been updated?

CVE-2026-31812 was published on March 10, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

Not in CISA KEV

CVE-2026-31812 — quinn-proto

Fix: quinn-rs/quinn#2559

CVE-2026-31812 is a CWE-248 vulnerability in quinn-proto. A fix is available for quinn-proto — see the affected versions and patch details below.

Quinn affected by unauthenticated remote DoS via panic in QUIC transport parameter parsing

Also known asGHSA-6xvm-j4wr-6v98RUSTSEC-2026-0037

Published

Mar 10, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-31812.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

🦀quinn-proto

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

Description

Summary

A remote, unauthenticated attacker can trigger a denial of service in applications using vulnerable quinn versions by sending a crafted QUIC Initial packet containing malformed quic_transport_parameters. In quinn-proto parsing logic, attacker-controlled varints are decoded with unwrap(), so truncated encodings cause Err(UnexpectedEnd) and panic. This is reachable over the network with a single packet and no prior trust or authentication.

Details

The issue is panic-on-untrusted-input in QUIC transport parameter parsing. In quinn-proto (observed in quinn-proto 0.11.13), parsing of some transport parameters uses a fallible varint decode followed by unwrap(). For malformed/truncated parameter values, decode returns UnexpectedEnd, and unwrap() panics.

Observed output:

thread 'tokio-rt-worker' (2366474) panicked at quinn-proto/src/transport_parameters.rs:473:67:
called `Result::unwrap()` on an `Err` value: UnexpectedEnd

PoC

Reproduces against the upstream Quinn server example.

Start server:

cargo run --example server -- ./

Prepare PoC client environment:

python3 -m venv .venv
source .venv/bin/activate
pip install aioquic

Run PoC script attack.py against server QUIC listener (default example target shown):

python attack.py

Observed output

thread 'tokio-rt-worker' (2366903) panicked at quinn-proto/src/transport_parameters.rs:473:67:
called `Result::unwrap()` on an `Err` value: UnexpectedEnd

Impact

Vulnerability type: Remote Denial of Service (panic/crash) Attack requirements: Network reachability to UDP QUIC listener Authentication/privileges: None Who is impacted: Any server/application using affected quinn/quinn-proto versions where this parse path is reachable; process-level impact depends on integration panic handling policy

This vulnerability was originally submitted by @revofusion to the Ethereum Foundation bug bounty program

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`quinn-proto`	all versions	0.11.14`cargo update -p quinn-proto --precise 0.11.14`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for quinn-proto, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update quinn-proto to 0.11.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-31812 is resolved across your whole dependency graph.
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 HatImportant

The availability impact of this flaw is limited to specific services on Red Hat systems. Host system availability is not at risk.

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 CVE-2026-31812 (CC BY 4.0)

Product	Fixed in	Advisory
Logging Subsystem for Red Hat OpenShift 6.4	`openshift-logging/vector-rhel9:1780052069`	RHSA-2026:22862
Red Hat Ansible Automation Platform 2.6	`ansible-automation-platform-26/lightspeed-chatbot-rhel9:1777398576`	RHSA-2026:13545
Red Hat OpenShift AI 2.25	`rhoai/odh-fms-guardrails-orchestrator-rhel9:1791535252`	RHSA-2026:87410
Red Hat OpenShift AI 3.3	`rhoai/odh-model-registry-job-async-upload-rhel9:1778596806`	RHSA-2026:19712
Red Hat Trusted Artifact Signer 1.3	`rhtas/tuffer-rhel9:1773307309`	RHSA-2026:5459

Frequently Asked Questions

### Summary A remote, unauthenticated attacker can trigger a denial of service in applications using vulnerable `quinn` versions by sending a crafted QUIC Initial packet containing malformed `quic_transport_parameters`. `In quinn-proto` parsing logic, attacker-controlled varints are decoded with `unwrap()`, so truncated encodings cause `Err(UnexpectedEnd)` and `panic`. This is reachable over the network with a single packet and no prior trust or authentication. ### Details The issue is panic-on-untrusted-input in QUIC transport parameter parsing. In `quinn-proto` (observed in `quinn-proto 0.1

O3 Security · Impact-Aware SCA

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