auto client cert connection reuse mixup
Only affects curl 8.21.0 through 8.22.0 built with the Schannel TLS backend on Windows. curl rates it Low, below its CVSS score. Fixed in 8.23.0.
- 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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? →
- Unclear
- 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: none
- Automatable: yes
- Technical impact: partial
Summary
libcurl's connection cache match function never considers the automatic client certificate option, so a cached, already authenticated Schannel connection can be handed to a transfer that got redirected to a different origin, even though the code explicitly switched off the auto client cert option for that transfer to prevent exactly this.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- 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-2026-86415
What does this mean?
A cached connection that is already authenticated can be reused for a redirected transfer to a different origin. This can leak data that was sent over the connection (CWE-201, Information Exposure Through Sent Data).Source: curl.se, curl.se
Am I affected, and how do I check?
Affects curl 8.21.0 through 8.22.0 only when built with Schannel as the TLS backend, which is available only on Windows. To check a installation, run curl --version and look at the TLS backend it reports.Source: curl.se, curl.se
What should I do about it?
Upgrade to curl 8.23.0, which contains the fix. If an upgrade is not possible, the advisory's workaround is to build curl with a different TLS backend.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. No public exploit code is tracked.Source: cve.now feed data