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Set-Cookie denial of service

Project curl Security Advisory, June 27th 2022 - Permalink


A malicious server can serve excessive amounts of Set-Cookie: headers in a HTTP response to curl and curl stores all of them. A sufficiently large amount of (big) cookies make subsequent HTTP requests to this, or other servers to which the cookies match, create requests that become larger than the threshold that curl uses internally to avoid sending crazy large requests (1048576 bytes) and instead returns an error.

This denial state might remain for as long as the same cookies are kept, match and haven't expired. Due to cookie matching rules, a server on can set cookies that also would match for, making it it possible for a "sister server" to effectively cause a denial of service for a sibling site on the same second level domain using this method.


CVE-2022-32205 was introduced in commit ed35d6590e72c23c, shipped in curl 7.71.0 with the introduction of the "dynbuf" internally. Before this change, curl had no limit in how large HTTP request it could generate.

CWE-770: Allocation of Resources Without Limits or Throttling

Severity: Low


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


We introduce several new limits and thresholds for cookies:


A - Upgrade curl to version 7.84.0

B - Apply the patch to your local version

C - Do not use cookies


This issue was reported to the curl project on May 13, 2022. We contacted distros@openwall on June 20.

libcurl 7.84.0 was released on June 27 2022, coordinated with the publication of this advisory.


Thanks a lot!