---
id: "CVE-2026-95691"
page: "https://infrastack.ai/live/CVE-2026-95691"
kind: "vulnerability"
aliases: ["CVE-2026-95691"]
title: "OpenSSL QUIC client: retransmitted CRYPTO frame causes use-after-free read (DoS or one-byte leak)"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "openssl", "fixed": ["3.5.10", "4.0.4", "4.1.1"], "affected": ">= 3.5.0, < 3.5.10; >= 4.0.0, < 4.0.4; >= 4.1.0, < 4.1.1", "ecosystem": "vendor"}]
ecosystems: []
tags: ["c", "http3", "openssl", "openssl-quic-client", "package", "quic"]
not_affected_if: ["fips-module", "no-quic-client", "tcp-only"]
published_at: "2026-11-10T19:21:39+00:00"
first_seen_at: "2026-11-10T19:25:22+00:00"
updated_at: "2026-11-10T20:46:06+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-95691", "first_seen_at": "2026-11-10T19:25:22+00:00"}, {"source": "analyst", "url": "https://openssl-library.org/news/vulnerabilities/", "first_seen_at": "2026-11-10T20:34:38+00:00", "cites": ["https://openssl-library.org/news/vulnerabilities/"]}]
exploit_sources: []
---

# OpenSSL QUIC client: retransmitted CRYPTO frame causes use-after-free read (DoS or one-byte leak)

Link for people: https://infrastack.ai/live/CVE-2026-95691 (this .md is for agents)

A retransmitted QUIC CRYPTO frame can free memory that the TLS layer still points to, causing a use-after-free read in the OpenSSL QUIC client. A malicious QUIC server can crash the client or leak one byte of heap memory.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:openssl affected >= 3.5.0, < 3.5.10; >= 4.0.0, < 4.0.4; >= 4.1.0, < 4.1.1 fixed 3.5.10, 4.0.4, 4.1.1

## How to check

- Run 'openssl version' and check the library your app links against: affected are 4.1.0, 4.0.0-4.0.3 and 3.5.0-3.5.9.
- Only matters if your code or a dependency uses OpenSSL's QUIC client (SSL_new with the QUIC client method, i.e. outbound HTTP/3 or QUIC connections made through OpenSSL). TCP TLS and the FIPS module are not affected.
- Also check if you ship a distro or vendored OpenSSL build: confirm with the distributor that the backport of the fix is in. Versions outside 3.5, 4.0 and 4.1 are not listed by the vendor; confirm with them.

## Fix

Upgrade OpenSSL to 4.1.1 (4.1.x), 4.0.4 (4.0.x) or 3.5.10 (3.5.x).

## Timeline

- 2026-11-10T19:25:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-95691
- 2026-11-10T20:34:38+00:00 analyst https://openssl-library.org/news/vulnerabilities/ — Read OpenSSL vulnerabilities page (vendor): affected/fixed versions, vendor severity Low (triage had high, lowered per vendor rating); commits confirm fix by range locking, reported by Filipe Casal. No X/web search done (web-cli unavailable); no exploitation or PoC seen.

## Documents

- [advisory] OpenSSL vulnerabilities: CVE-2026-95691 https://openssl-library.org/news/vulnerabilities/
- [fix] Patch: github.com https://github.com/openssl/openssl/commit/dd90ceb99a3c2ddba336bb4a00be9ebabd84c2a1
- [fix] Patch: github.com https://github.com/openssl/openssl/commit/ec9d4de9d03989b29db5a3d7efdb4c285deaf386
- [fix] Patch: github.com https://github.com/openssl/openssl/commit/f6244675833e097c2429a40d1b206d95385bd42f

## From the sources

Issue summary: A retransmitted QUIC CRYPTO frame can release packet storage
while the TLS record layer retains a direct pointer into that storage causing
use after free.

Impact summary: A malicious QUIC server can cause a heap-use-after-free read
in the OpenSSL QUIC client. The server can also identify one allocator-adjacent
byte through the client's protected Handshake response.

CWE: CWE-416: Use After Free

Description: During CRYPTO stream processing, a pointer into the first frame's
memory on the stream is lent to the TLS handshake processing. The memory
must remain stable until it is processed and released. However the processing
of retransmitted CRYPTO frames could release the memory if the retransmitted
frame fully overlapped the existing frame. This then causes use-after-free read
when the TLS handshake processing continues.

The use-after-free read can lead to a Denial-of-Service of the client
application or a minor leak of information about the heap memory contents
that might be overwritten with other data, subsequently allocated by
the application, to the peer.

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

---

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