🛡️ CVE-2026-44433 — quicly

🟡 CVSS 5.3 — Medium ✅ No Known Exploit CWE-400 NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, an adversarial peer could send a STREAM frame carrying just one byte at the largest offset being permitted to obtain additional flow control credit, which under certain circumstances could lead to a Denial of Service. Assuming the application prepares a receive buffer for storing all data that arrive out-of-order, up to the largest offset being received, this behavior could lead to the application allocating large amount of memory with the peer sending only a handful of packets, resulting in memory exhaustion. In addition to the receive buffer allocation strategy, the severity of this vulnerability depends on how the application controls the stream concurrency. In case of the H2O HTTP server, under its default setting, this bug increases the maximum amount of memory allocated per connection by about 4 times. This issue has been fixed by commit 8b178e6.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

Weakness class

CVE-2026-44433 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

CVE-2026-44433 is recorded against 1 package.

  • quicly (fixed in 2026-05-29)

Timeline and source

Published on 16 July 2026 and last revised on 6 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE CWE-400
Public Exploit ✅ No
Source NVD
Published 2026-07-16
Updated 2026-08-11
Modified 2026-08-06

Affected Packages

Software From version Fixed in
quicly — 2026-05-29

Similar Threats

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