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OpenAdvisories

Description

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.

Affected products

VendorProductAffectedFixed
OpenSSL OpenSSL 4.0.0 – < 4.0.3, 3.6.0 – < 3.6.5, 3.5.0 – < 3.5.9, 3.4.0 – < 3.4.8 4.0.3

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 openssl 3.6.5-1 —
Debian 13 openssl 3.5.7-1~deb13u3 —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 edk2 +1 No fix yet —
Ubuntu 26.04 LTS edk2 +1 No fix yet —
Ubuntu 26.04 LTS openssl 3.5.5-1ubuntu3.6 USN-8847-1
Ubuntu 24.04 LTS openssl 3.0.13-0ubuntu3.16 USN-8847-1
Ubuntu 22.04 LTS openssl 3.0.2-0ubuntu1.30 USN-8847-1
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 22.04 LTS nodejs No fix yet —
ReleasePackageFixed inAdvisory
Red Hat Hardened Images 1 openssl +10 3.5.9-0.1.hum1 RHSA-2026:74166, RHSA-2026:74162

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 10 openssl +3 1:3.5.9-1.el10_3 RLSA-2026:98588
Rocky Linux 9 openssl +3 1:3.5.9-1.el9_9 RLSA-2026:98484
ReleasePackageFixed inAdvisory
SLES 15 SP7 openssl-3 3.5.0-150700.5.53.2 SUSE-SU-2026:4414-1
Show 3 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 openssl-3 3.5.0-160000.11.1 SUSE-SU-2026:24245-1
SLES 16.0 openssl-3 3.5.0-160000.11.1 SUSE-SU-2026:24245-1
SLE Micro 6.2 openssl-3 3.5.0-160000.11.1 SUSE-SU-2026:24188-1
ReleasePackageFixed inAdvisory
openSUSE Leap 16.0 openssl-3 3.5.0-160000.11.1 openSUSE-SU-2026:22102-1
ReleasePackageFixed inAdvisory
Alpine v3.21 openssl 3.3.7-r2 —

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 openssl +5 1:3.5.8-1.amzn2023.0.3 ALAS2023-2026-3204

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 openssl 3.3.7-7 —
Azure Linux 3 rust +3 No fix yet —

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling openssl-4.0 +2 4.0.3-r0 —

Advisories 11

References