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
foo.example.com can set cookies that also would match for
bar.example.com, 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
- Affected versions: curl 7.71.0 to and including 7.83.1
- Not affected versions: curl < 7.71.0 and curl >= 7.84.0
- Introduced-in: https://github.com/curl/curl/commit/ed35d6590e72c23c
libcurl is used by many applications, but not always advertised as such!
We introduce several new limits and thresholds for cookies:
Send no more than 150 cookies per request
Cap the max length used for an outgoing
Cookie:header to 8K
Cap the max number of accepted
Set-Cookie:header fields to 50
A - Upgrade curl to version 7.84.0
B - Apply the patch to your local version
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.
- Reported-by: Harry Sintonen
- Patched-by: Daniel Stenberg
Thanks a lot!