# CVE-2026-75804: OpenSSL QUIC stack memory exhaustion in flow control

Source: https://junglewise.ai/threats/cve-2026-75804-issue-summary-openssl-quic-stack-does-not-enforce-connection  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-75804 · Severity: info · Published 2026-09-29

OpenSSL's QUIC implementation (used for secure, low-latency network connections) fails to enforce connection-level flow control limits on multiple streams. A remote attacker can exploit this to force the server to allocate up to 100 MB of memory per connection instead of the expected 768 KB, causing memory exhaustion and potential service degradation.

Technologies: [OpenSSL](https://junglewise.ai/threats/technologies/openssl). Vendors: [OpenSSL](https://junglewise.ai/threats/vendors/openssl).

## Quick answers

**Is CVE-2026-75804 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-75804 being exploited in the wild.

**How severe is CVE-2026-75804?** Informational severity, published 29 September 2026.

**Which products and versions are affected?** OpenSSL versions with QUIC support prior to fix.

**Is there a fix for CVE-2026-75804?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-75804 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-75804?** Check whether you run OpenSSL at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability stems from incomplete validation of QUIC flow control: the stack enforces per-stream limits but omits connection-level limits. An attacker opens multiple streams (up to 200 total, mixing bidirectional and unidirectional), keeps each stream under its individual limit but collectively exceeds the connection limit, and avoids sending zero-offset bytes to prevent data consumption. This causes unbounded heap allocation—up to 100 MB per connection versus the 768 KB default window.

## Affected products

- OpenSSL OpenSSL versions with QUIC support prior to fix

## Timeline

- 2026-09-29: disclosed: CVE-2026-75804 published

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