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Fencer Intel
low 3.7

CVE-2026-35191 json

QUIC Unvalidated Amplification Credit may be Over Accounted

published last mo. modified last mo. also EUVD-2026-89002

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in its unvalidated credit computation, leading to a violation of the RFC 9000 unvalidated connection amplification limit of 3 times the amount of data received.

Impact summary: A remote attacker able to spoof packets to a server using the OpenSSL QUIC implementation might use the server for an amplification of a DDoS attack.

CWE: CWE-440: Expected Behavior Violation

Description: OpenSSL's QUIC stack, when operating as a server, enforces client address validation (RFC 9000, Section 8), to confirm the peer address is not used for a traffic amplification attack. If this feature is disabled on the server, the QUIC stack limits the amount of server data that can be sent to 3 times the amount of data received from the peer address, until such time as the TLS handshake is completed.

The OpenSSL QUIC server, when operating in non-validation mode, adds the length of the whole datagram received to the unvalidated credit limit when processing each QUIC packet in the datagram. A remote peer may, after establishing a connection with an initial client hello frame, send a subsequent datagram containing multiple QUIC packets, leading the server to account the entire datagram length for each packet in the datagram, resulting in the server believing that the peer has sent more data than it actually has, thereby violating the 3x amplification limit mandated by the RFC.

FIPS impact: no As the QUIC stack lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.

Patch / fix

  • OpenSSL OpenSSL 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-2026-35191

  • openssl Ubuntu 26.04 LTS 3.5.5-1ubuntu3.6

ubuntu advisories UBUNTU-CVE-2026-35191

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

Is CVE-2026-35191 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2026-35191 updated cvss 3.7

openssl: openssl: Traffic amplification Denial of Service via QUIC packet over-accounting

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Enterprise Linux 9 openssl, shim-x64, edk2-ovmf, shim-aa64, edk2-tools, edk2-aarch64, +9 more Red Hat Enterprise Linux 10 shim 16.1-4.el10, openssl 3.5.8-1.el10_2, edk2 20251114-5.el10_2.2, 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
    affected: workaround, no fix available “If QUIC is not required, disable it in the application or proxy. Prefer leaving QUIC address validation enabled (OpenSSL default). Restrict untrusted UDP/QUIC peers.”
  • 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 proxy. Prefer leaving QUIC address validation enabled (OpenSSL default). Restrict untrusted UDP/QUIC peers.” 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 Hardened Images unbound 1.26.1-1.hum1 Red Hat JBoss Core Services jbcs-httpd24-openssl, jbcs-httpd24-openssl-libs, jbcs-httpd24-openssl-perl 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
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CISA ADP 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • OpenSSL OpenSSL

Classification

Weakness
  • CWE-440 Expected Behavior Violation
Technology feeds

References

Sources

Fencer Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.