CVE-2026-11856

Publication date 24 June 2026

Last updated 25 August 2026

Ubuntu priority

Cvss 3 Severity Score

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`.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
curl	26.04 LTS resolute	Fixed 8.18.0-1ubuntu2.4
	25.10 questing	Ignored end of life, was ignored [changes too intrusive]
	24.04 LTS noble	Fixed 8.5.0-2ubuntu10.12
	22.04 LTS jammy	Fixed 7.81.0-1ubuntu1.26
	20.04 LTS focal	Fixed 7.68.0-1ubuntu2.25+esm6
	18.04 LTS bionic	Fixed 7.58.0-2ubuntu3.24+esm11
	16.04 LTS xenial	Fixed 7.47.0-1ubuntu2.19+esm18
	14.04 LTS trusty	Fixed 7.35.0-1ubuntu2.20+esm22

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Notes

kkernick

This fix is predicated on Curl_creds, which was introduced in 8f71d0f in 8.21, and several subsequent commits adding to it.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
curl	Upstream: 5c6b488

Severity score breakdown

CVSS version: CVSS v3.0

Base score 9.8 · Critical

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality impact	High
Integrity impact	High
Availability impact	High

Scores

Parameter	Value
Base score	9.8 · Critical
Exploitability score	-
Impact score	-