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Vulnerability record · CVE-2026-11856 · published 3 July 2026

CVE-2026-11856: Haxx curl authentication bypass by capture-replay vulnerability

Haxx · Curl

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`.

9.8 CVSS 3.1 Critical EPSS 0.69% · top 49.2% CWE-294 · Authentication bypass by capture-replay
9.8CVSS 3.1 base score
0.69%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
15 Sep 2026Last modified by NVD

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`.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://curl.se/docs/CVE-2026-11856.html PatchVendor Advisory
https://curl.se/docs/CVE-2026-11856.json Vendor Advisory
https://hackerone.com/reports/3793260 ExploitIssue TrackingThird Party Advisory
https://hackerone.com/reports/3793260 ExploitIssue TrackingThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2026-19931Haxx curl vulnerabilityA flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is do…EPSS 0.75%9.8CVE-2026-9079Haxx curl insufficiently protected credentials vulnerabilitylibcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get …EPSS 0.58%9.8CVE-2026-8925Haxx curl double free vulnerabilityThe curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing the pointer in between, making…EPSS 1.1%9.8CVE-2026-10536Haxx curl use after free vulnerabilityA use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CUR…EPSS 0.60%9.8CVE-2022-32221Haxx curl information exposure vulnerabilityWhen doing HTTP(S) transfers, libcurl might erroneously use the read callback (`CURLOPT_READFUNCTION`) to ask for data to send, even when the `CURLOP…EPSS 4.4%9.8CVE-2022-32207Haxx curl incorrect default permissions vulnerabilityWhen curl < 7.84.0 saves cookies, alt-svc and hsts data to local files, it makes the operation atomic by finalizing the operation with a rename from …EPSS 7.7%9.8CVE-2016-4606Haxx curl vulnerabilityCurl before 7.49.1 in Apple OS X before macOS Sierra prior to 10.12 allows remote or local attackers to execute arbitrary code, gain sensitive inform…EPSS 3.4%9.8CVE-2019-5481Haxx curl double free vulnerabilityDouble-free vulnerability in the FTP-kerberos code in cURL 7.52.0 to 7.65.3.EPSS 7.5%

Source: NIST National Vulnerability Database (record CVE-2026-11856), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.