CVE intelligence and bounded remediation
CVE-2026-6253 — curl might erroneously pass on credentials for a first proxy to a second proxy
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
- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Published
- 2026-05-13
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-522
Affected products
- haxx / curl
Matched remediation archetype
Information disclosure and sensitive data exposure
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Trace sensitive data through responses, errors, logs, metrics, traces, caches, exports, files, backups, and client bundles.
- Identify affected subjects, tenants, retention windows, access controls, and downstream copies without opening unnecessary sensitive records.
- Review metadata, timing, status, length, and existence signals as well as direct content disclosure.
Remediate safely
- Minimize collection and output, apply field-level authorization and redaction at a centralized boundary, and return generic external errors.
- Remove secrets and sensitive data from logs, artifacts, URLs, caches, and client-side bundles; rotate credentials that may have been exposed.
- Update the affected component and add synthetic-data tests for response, error, observability, and export paths.
Authoritative sources
Complete CVE record and remediation plan
The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.