# CVE-2026-11352: curl QUIC infinite loop in UDP receive function

Source: https://junglewise.ai/threats/cve-2026-11352-curl-quic-infinite-loop-in-udp-receive-function  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-03. Updated: 2026-07-03  
License: CC BY 4.0 with a link back

CVE-2026-11352 · Severity: info · CVSS 0 · Published 2026-07-03

A vulnerability in the curl data transfer tool and library can allow a malicious website to freeze the application. By sending a continuous stream of empty data packets over an HTTP/3 connection, a server can force the curl client into an infinite loop. This results in a denial of service where the application becomes unresponsive and stops processing other tasks.

## Quick answers

**Is CVE-2026-11352 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-11352 being exploited in the wild.

**How severe is CVE-2026-11352?** Informational severity, with a CVSS score of 0, published 3 July 2026.

**Which products and versions are affected?** curl curl 8.18.0 to 8.20.0; curl libcurl 8.18.0 to 8.20.0.

**Is there a fix for CVE-2026-11352?** A patch was published on 2026-06-24: Fixed in version 8.21.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-11352 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-11352?** Check whether anything you run is named in the advisory. 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

A denial of service vulnerability exists in curl's QUIC implementation (CWE-835). The root cause is located in the UDP receive helper function, which discards zero-length UDP datagrams without counting them toward the per-call packet processing budget. A malicious HTTP/3 server can exploit this by continuously streaming empty datagrams, causing the client to enter a busy-loop and indefinitely stall. This issue specifically affects platforms utilizing the recvmmsg() system call. The vulnerability was introduced in version 8.18.0 and is resolved in version 8.21.0.

## Affected products

- curl curl 8.18.0 to 8.20.0
- curl libcurl 8.18.0 to 8.20.0

## Timeline

- 2026-06-05: disclosed: Reported via HackerOne
- 2026-06-24: patched: Fixed in version 8.21.0
- 2026-06-24: advisory: Project advisory published
- 2026-07-03: other: NVD publication date

## References

- [https://curl.se/docs/CVE-2026-11352.html](https://curl.se/docs/CVE-2026-11352.html)
- [https://curl.se/docs/CVE-2026-11352.json](https://curl.se/docs/CVE-2026-11352.json)
- [https://hackerone.com/reports/3783438](https://hackerone.com/reports/3783438)