Skip to content
Fencer Vulns
high 7.5

CVE-2026-84784 json

QUIC: Unbounded RETIRE_CONNECTION_ID Backlog

published 2026-09-29 40 d ago modified 2026-10-08 32 d ago also EUVD-2026-89015

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

Issue summary: A malicious remote peer may flood the local QUIC stack with NEW_CONNECTION_ID frames by avoiding a limit check on how many connection IDs the remote QUIC stack can use.

Impact summary: The local QUIC stack sends a RETIRE_CONN_ID frame for every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_ID frame is dispatched via the Control Frame Queue (CFQ). If the remote peer also withholds ACKs, then it can force the local stack to allocate ~400MB (depending on ACK delay).

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanism by which a remote peer can notify the local QUIC stack to change the destination connection ID (a.k.a. CID) the local stack uses to identify the connection at the remote peer. Each CID is associated with a sequence number. The sequence number is transmitted in NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CID which is being either associated with a connection or retired.

The remote peer sends a NEW_CONNECTION_ID frame to let the local stack know a new CID is being associated with an existing connection. The NEW_CONNECTION_ID frame carries the new CID, its sequence number, and the retire-prior-to number. The retire-prior-to identifies existing CIDs that are to be retired. The local QUIC stack must send a RETIRE_CONNECTION_ID for every destination CID whose sequence number is less than retire-prior-to. The CID becomes retired after the local stack receives an ACK for its RETIRE_CONNECTION_ID frame.

Although the OpenSSL QUIC stack supports at most one destination CID for every connection, it can be tricked into processing more than one RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUIC stack currently retires the destination CID as soon as it receives the NEW_CONNECTION_ID, while in fact the destination CID must be retired after an ACK for the RETIRE_CONNECTION_ID frame is received. Correcting the flawed logic also fixes the backlog growth.

[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids

FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

Patch / fix

  • OpenSSL OpenSSL 3.4.8, 3.5.9, 3.6.5, 4.0.3
  • openssl Debian 13 3.5.7-1~deb13u3
  • openssl Debian 14 3.6.5-1

debian advisories DEBIAN-CVE-2026-84784

  • openssl Ubuntu 26.04 LTS 3.5.5-1ubuntu3.6

ubuntu advisories UBUNTU-CVE-2026-84784

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl3 hummingbird 1 3.5.9-0.1.hum1
  • openssl3-libs hummingbird 1 3.5.9-0.1.hum1
  • openssl3-devel-engine hummingbird 1 3.5.9-0.1.hum1
  • openssl hummingbird 1 3.5.9-0.1.hum1
  • openssl-libs hummingbird 1 3.5.9-0.1.hum1
  • openssl-perl hummingbird 1 3.5.9-0.1.hum1
  • openssl-config-fips hummingbird 1 3.5.9-0.1.hum1
  • openssl-devel-engine hummingbird 1 3.5.9-0.1.hum1

red hat advisories RHSA-2026:74166RHSA-2026:74162

  • openssl-3 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.5.0-160000.11.1
  • openssl-3 SLE Module for Basesystem 15 SP7 3.5.0-150700.5.53.2

suse advisories SUSE-SU-2026:24188-1SUSE-SU-2026:24245-1SUSE-SU-2026:4414-1

  • openssl-3 openSUSE Leap 16.0 3.5.0-160000.11.1

opensuse advisories openSUSE-SU-2026:22102-1

  • openssl Alpine 3.21 3.3.7-r2

alpine advisories ALPINE-CVE-2026-84784

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl Azure Linux 3.0 3.3.7-7

azure linux advisories AZL-105585

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-84784 updated cvss 5.3

openssl: OpenSSL: Denial of Service via unbounded QUIC connection identifier backlog

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Enterprise Linux 9 openssl, shim-x64, shim-aa64, openssl-libs, openssl-perl, compat-openssl11, +5 more Red Hat Enterprise Linux 10 shim 16.1-4.el10, openssl 3.5.8-1.el10_2, edk2 20260221-7.el10_3.1, shim-unsigned-x64 16.1-1.el10, shim-unsigned-aarch64 16.1-2.el10 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9 Red Hat Satellite 6 puppet-agent, openvox-agent 8.28.1-1.el9sat
    +1 more products
    Red Hat Self-service automation portal 2 ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available “If QUIC is not required, disable it in the application or reverse proxy. Restrict untrusted QUIC/UDP peers that can complete or attempt a handshake.”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-core-bff-rhel9, rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-maas-rhel9, rhoai/odh-mod-arch-automl-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-mlflow-rhel9, +6 more
    under investigation
  • Red Hat Hardened Images openssl 3.5.9-0.1.hum1, openssl3 3.5.9-0.1.hum1, openssl-libs 3.5.9-0.1.hum1, openssl-perl 3.5.9-0.1.hum1, openssl3-libs 3.5.9-0.1.hum1, openssl-config-fips 3.5.9-0.1.hum1, +3 more
    fixed: vendor fix “If QUIC is not required, disable it in the application or reverse proxy. Restrict untrusted QUIC/UDP peers that can complete or attempt a handshake.” RHSA-2026:74162
  • Red Hat Enterprise Linux 6 openssl, openssl-perl, openssl 3.5.8-1.el10_2 Red Hat Enterprise Linux 7 ovmf, OVMF, shim, AAVMF, mokutil, openssl, +6 more Red Hat Enterprise Linux 8 openssl, shim-x64, edk2-ovmf, shim-aa64, shim-ia32, edk2-aarch64, +13 more Red Hat Enterprise Linux 9 edk2-ovmf, edk2-tools, edk2-aarch64, edk2 20260221-7.el10_3.1 Red Hat Hardened Images unbound 1.26.1-1.hum1 Red Hat JBoss Core Services jbcs-httpd24-openssl, jbcs-httpd24-openssl-libs, jbcs-httpd24-openssl-perl
    +1 more products
    Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-kube-rbac-proxy-rhel9, rhoai/odh-maas-controller-rhel9, rhoai/odh-mlflow-operator-rhel9, rhoai/odh-model-controller-rhel9, rhoai/odh-ogx-k8s-operator-rhel9, +14 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
40 d ago

Exploit prediction

0.61% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • OpenSSL OpenSSL

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.