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CVE-2026-75804

5.3 · MEDIUM

Issue summary: OpenSSL QUIC stack does not enforce connection level flow control for streams.

Published Sep 29, 2026opensslCWE-770EPSS 0.53%

Overview

CVE-2026-75804 is a medium-severity vulnerability affecting openssl openssl. It was published on September 29, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Issue summary: OpenSSL QUIC stack does not enforce connection

level flow control for streams. Remote peers may send more bytes

as long as they fit within the stream flow control limits.

Impact summary: A malicious remote peer may exploit the lack of connection

flow control for streams to make the QUIC stack receive ~100MB of memory

instead of 768 KiB (default flow control window size).

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

Description: The local QUIC stack advertises two flow control limits

to its remote peer: stream flow control limit and connection flow

control limit. The remote peer must follow both limits when transmitting

stream data.

Whenever the local QUIC stack receives a stream frame, it validates

that the size of the received stream frame stays within flow control limits.

If either limit is exceeded (stream level or connection level), then

the QUIC stack must close the connection with a flow control error.

The vulnerable OpenSSL QUIC stack en

Remediation

Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
opensslopenssl>= 3.4.0, < 3.4.8Affected

References

GitHubgithub.com/openssl/openssl/commit/2e8f54666b3fb7b05ff5f58aa6cac9285163654eGitHubgithub.com/openssl/openssl/commit/4533ee8a5686c953ed3b644738ac4bdf20806538GitHubgithub.com/openssl/openssl/commit/64d3102fb5b54311e92517f26ba00169d719e74aGitHubgithub.com/openssl/openssl/commit/f9eaecf5bdd6692da052bc65b0332af2a938ac03Refopenssl-library.org/news/secadv/20260929.txt

How CyberStrike helps

Frequently asked questions

What is CVE-2026-75804?

CVE-2026-75804 is a medium-severity vulnerability affecting openssl openssl. It was published on September 29, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-75804?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-75804?

Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-75804?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-75804 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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