# CVE-2026-11586: curl memory exhaustion in WebSocket PING handling

Source: https://junglewise.ai/threats/cve-2026-11586-curl-memory-exhaustion-in-websocket-ping-handling  
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-2026-11586 · Severity: info · Published 2026-07-03

curl is a widely used tool and library for transferring data over various network protocols. A vulnerability in its WebSocket implementation allows a malicious server to crash the application or the entire system by flooding it with specific messages. This results in a denial-of-service condition where the software runs out of memory and stops functioning.

## Quick answers

**Is CVE-2026-11586 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-11586 being exploited in the wild.

**How severe is CVE-2026-11586?** Informational severity, published 3 July 2026.

**Which products and versions are affected?** curl curl 8.16.0 to 8.20.0.

**Is there a fix for CVE-2026-11586?** A patch was published on 2026-06-24: Fixed in curl version 8.21.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-11586 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-11586?** 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 resource exhaustion vulnerability (CWE-770) exists in curl's WebSocket implementation. By default, curl automatically responds to WebSocket PING frames with PONG frames. However, the library lacks an upper bound on memory allocation for these unacknowledged outgoing frames. A malicious server can exploit this by sending a rapid sequence of PING messages, causing curl to allocate increasing amounts of memory until it or the host application crashes due to an out-of-memory (OOM) condition. The issue is fixed in version 8.21.0, and a workaround exists by disabling automatic PING responses using the CURLWS_NOAUTOPONG option.

## Affected products

- curl curl 8.16.0 to 8.20.0

## Timeline

- 2026-06-08: disclosed: Reported to curl project via HackerOne
- 2026-06-24: patched: Fixed in curl version 8.21.0
- 2026-06-24: advisory: Project advisory published

## References

- [https://curl.se/docs/CVE-2026-11586.html](https://curl.se/docs/CVE-2026-11586.html)
- [https://curl.se/docs/CVE-2026-11586.json](https://curl.se/docs/CVE-2026-11586.json)
- [https://hackerone.com/reports/3788931](https://hackerone.com/reports/3788931)