CVE-2026-11856 cross-origin Digest auth state leak
libcurl leaks Digest authentication headers to unintended hosts when reusing handles, potentially exposing credentials to attackers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-11856?
CVE-2026-11856 is a critical vulnerability in Haxx Curl, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Authorization:` header field meant for `hostA`, to `hostB`.
Weakness: CWE-294
Which versions are affected by CVE-2026-11856?
It affects 1 product.
Products include Haxx Curl.
How do I fix CVE-2026-11856?
Upgrade to a fixed version.
Is CVE-2026-11856 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-11856 exists.
Other vulnerabilities in Haxx Curl
Sources
Also known as ALPINE-CVE-2026-11856, AZL-91803, AZL-91830, BELL-CVE-2026-11856, CLSA-2026-1783703539, CLSA-2026-1783705168 and 20 more.