Medium [CVE-2026-11856] Information disclosure via incorrect Digest authentication header reuse
This medium-severity Red Hat Linux advisory covers CVE-2026-11856 affecting Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
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Summary
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`. A flaw was found in curl.
This could lead to unintended information disclosure, potentially allowing an attacker to gain unauthorized access to sensitive data. This Moderate-severity flaw in `libcurl` can lead to information disclosure when an application reuses a `libcurl` handle for transfers to different HTTP origins while using Digest authentication.
The vulnerability arises from `libcurl` incorrectly sending the authentication header intended for the initial origin to a subsequent, different origin. This could expose sensitive authentication data to an unintended recipient, potentially compromising user credentials or session information.
Affected products named by the advisory: Red Hat Hardened Images; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; and 4 more.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
- curl-main-8.21.0-0.1.hum1
- rust-main-1.96.1-1.hum1
- RHSA-2026:29017
- RHSA-2026:34975
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Correct usage of the library: Create a fresh handle for a different origin, or explicitly clear authentication-related state before reuse: ```c // req.A curl = curl_easy_init(); ... curl_easy_cleanup(curl); // req.B curl = curl_easy_init(); ... curl_easy_cleanup(curl); ``` Fixed in libcurl 8.21.0; affected range: 7.10.6 – 8.20.0
Official advisory · high-confidence parse· fetched 4 hours ago·verify at source
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