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[ADVISORY] curl: CVE-2026-3783: token leak with redirect and netrc
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From: Daniel Stenberg via curl-library <curl-library_at_lists.haxx.se>
Date: Wed, 11 Mar 2026 07:54:44 +0100 (CET)
token leak with redirect and netrc
==================================
Project curl Security Advisory, March 11th 2026
[Permalink](https://curl.se/docs/CVE-2026-3783.html)
VULNERABILITY
-------------
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer
performs a redirect to a second URL, curl could leak that token to the second
hostname under some circumstances.
If the hostname that the first request is redirected to has information in the
used .netrc file, with either of the `machine` or `default` keywords, curl
would pass on the bearer token set for the first host also to the second one.
INFO
Date: Wed, 11 Mar 2026 07:54:44 +0100 (CET)
token leak with redirect and netrc
==================================
Project curl Security Advisory, March 11th 2026
[Permalink](https://curl.se/docs/CVE-2026-3783.html)
VULNERABILITY
-------------
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer
performs a redirect to a second URL, curl could leak that token to the second
hostname under some circumstances.
If the hostname that the first request is redirected to has information in the
used .netrc file, with either of the `machine` or `default` keywords, curl
would pass on the bearer token set for the first host also to the second one.
INFO
---- The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2026-3783 to this issue. CWE-522: Insufficiently Protected Credentials Severity: Medium AFFECTED VERSIONS ----------------- - Affected versions: curl 7.33.0 to and including 8.18.0 - Not affected versions: curl < 7.33.0 and >= 8.19.0 - Introduced-in: https://github.com/curl/curl/commit/06c1bea72faabb6fad4b7ef8 libcurl is used by many applications, but not always advertised as such! This bug is not considered a *C mistake*. It is not likely to have been avoided had we not been using C. This flaw also affects the curl command line tool. SOLUTION -------- curl 8.19.0 fixes this flaw - Fixed-in: https://github.com/curl/curl/commit/e3d7401a32a46516c9e5ee877 RECOMMENDATIONS --------------- We suggest you take one of the following actions immediately, in order of preference: A - Upgrade to curl and libcurl 8.19.0 B - Apply the patch and rebuild libcurl C - Avoid using Bearer tokens with redirects TIMELINE --------- It was reported to the curl project on March 3rd 2026. We contacted distros_at_openwall on March 8. libcurl 8.19.0 was released on March 11th 2026, coordinated with the publication of this advisory. CREDITS ------- - Reported-by: spectreglobalsec on hackerone - Patched-by: Daniel Stenberg Thanks a lot! -- / daniel.haxx.se || https://rock-solid.curl.dev -- Unsubscribe: https://lists.haxx.se/mailman/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2026-03-11