---
id: CVE-2026-35191
title: |-
  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 c…
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 c…
severity: none
cwe:
  - CWE-440
vendor: OpenSSL
product: OpenSSL
affected:
  - OpenSSL >= 4.0.0 < 4.0.3
  - OpenSSL >= 3.6.0 < 3.6.5
  - OpenSSL >= 3.5.0 < 3.5.9
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T16:17:07.490'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-35191'
references:
  - url: >-
      https://github.com/openssl/openssl/commit/0fe4442d4f8ea3af8a174046dae176e0d4717239
    label: openssl-security@openssl.org
  - url: >-
      https://github.com/openssl/openssl/commit/2de4c35fb13fc58f43fd8dc1d261700472ce72e5
    label: openssl-security@openssl.org
  - url: >-
      https://github.com/openssl/openssl/commit/e44292e58b090014232ef75bd400393851b24d1a
    label: openssl-security@openssl.org
  - url: 'https://openssl-library.org/news/secadv/20260929.txt'
    label: openssl-security@openssl.org
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-29T16:39:33.265Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.