Negotiate credentials sent to redirected origin
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- The rating the maker of the software gives it. Shown when it differs from the CVSS level.What do these mean? →
- Low (curl)
- Fix
- Fixed in 8.23.0
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: yes
- Technical impact: total
Summary
When using an ambient user in a first transfer doing Negotiate authentication and asked to follow redirects, curl could pass on its credential details to an unrelated second origin when asked to redirect there.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: poc · Automatable: yes · Technical impact: total
- Record last updated
Affected versions
- curl curl
From 8.22.0 · through 8.22.0; From 8.21.0 · through 8.21.0
References 3
hackerone.com
Questions about CVE-2026-86413
What does this mean?
When curl uses an ambient user with Negotiate authentication and follows a redirect to a URL that includes a user name and password, curl can pass its credential details to an unrelated second origin. The credentials go to a server other than the one the transfer was meant for.Source: curl.se, curl.se
Am I affected, and how do I check?
Versions curl 8.21.0 through 8.22.0 are affected, and the bug needs an ambient user with Negotiate authentication plus redirect following, where the redirect target includes user name and password. Check your curl version with the curl --version command and review whether your transfers use Negotiate with an ambient user and redirects.Source: curl.se, curl.se
What should I do about it?
Upgrade curl to version 8.23.0, which contains the fix. Until you can upgrade, avoid combining an ambient user with redirects.Source: curl.se, curl.se
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
Why is it rated 9.1 Critical?
CVSS scores the worst case at 9.1 (critical), while curl rates the issue Low because the vendor knows the triggering setup is narrow: it needs an ambient user, Negotiate authentication, and a redirect to a URL carrying credentials. The two ratings measure different things, so the gap is expected.Source: curl.se, curl.se