CVE-2026-6253
Description
curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while using the first proxy (using say `http://`), curl is asked to follow a redirect to a URL using another scheme (say `https://`), accessed using a second, different, proxy
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| debian | bookworm | affected | |
| debian | bullseye | affected | |
| debian | forky | fixed | 8.20.0~rc3-1 |
| debian | sid | fixed | 8.20.0~rc3-1 |
| debian | trixie | affected | |
| sles | affected | | |
| windows | affected | |
References
- https://curl.se/docs/CVE-2026-6253.html
- https://curl.se/docs/CVE-2026-6253.json
- https://hackerone.com/reports/3669637
- http://www.openwall.com/lists/oss-security/2026/04/29/11
- https://security-tracker.debian.org/tracker/CVE-2026-6253
- https://www.suse.com/security/cve/CVE-2026-6253.html
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-6253
CWEs
CWE-522
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.