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Date: Wed, 27 Mar 2024 07:58:09 +0100 (CET)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,, libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: CVE-2024-2398: HTTP/2 push headers

HTTP/2 push headers memory-leak

Project curl Security Advisory, March 27 2024 -


When an application tells libcurl it wants to allow HTTP/2 server push, and
the amount of received headers for the push surpasses the maximum allowed
limit (1000), libcurl aborts the server push. When aborting, libcurl
inadvertently does not free all the previously allocated headers and instead
leaks the memory.

Further, this error condition fails silently and is therefore not easily
detected by an application.


If a server sends many `PUSH_PROMISE` frames with an excessive amount of
headers, this can lead to multiple megabytes of memory leaked *per response*.

HTTP/2 server push is a relatively rarely used feature.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2024-2398 to this issue.

CWE-772: Missing Release of Resource after Effective Lifetime

Severity: Medium


- Affected versions: curl 7.44.0 to and including 8.6.0
- Not affected versions: curl < 7.44.0 and >= 8.7.0
- Introduced-in:

libcurl is used by many applications, but not always advertised as such!

This flaw is also accessible using the curl command line tool.


Starting in curl 8.7.0, the entire set of headers is freed appropriately on

- Fixed-in:


  A - Upgrade curl to version 8.7.0

  B - Apply the patch to your local version

  C - Make sure HTTP/2 push is not used


This issue was reported to the curl project on March 5, 2024. We contacted
distros@...nwall on March 19, 2024.

curl 8.7.0 was released on March 27 2024 around 07:00 UTC, coordinated with
the publication of this advisory.

The curl security team is not aware of any active exploits using this


- Reported-by: w0x42 on hackerone
- Patched-by: Stefan Eissing

Thanks a lot!



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