What’s Vulnerable › Vulnerabilities

CVE-2026-11856: cross-origin Digest auth state leak

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-03 · updated 2026-09-15
• Weakness: CWE-294

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`.

Affected products

• curl: from 7.10.6 before 8.21.0 — fixed in 8.21.0

How to fix

Upgrade to a fixed version: curl 8.21.0. Check the vendor advisory for mitigations.

References

• https://curl.se/docs/CVE-2026-11856.html
• https://curl.se/docs/CVE-2026-11856.json
• https://hackerone.com/reports/3793260
• https://hackerone.com/reports/3793260

Get alerted when CVE-2026-11856 or the next vulnerability affects your stack