{"id":"UBUNTU-CVE-2026-6253","details":"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","modified":"2026-05-20T22:02:00.436206587Z","published":"2026-04-29T14:00:00Z","related":["USN-8227-1"],"upstream":["CVE-2026-6253"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-6253"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-6253"},{"type":"REPORT","url":"https://curl.se/docs/CVE-2026-6253.html"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8227-1"}],"affected":[{"package":{"name":"curl","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/curl?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.32.0-1ubuntu1","7.33.0-1ubuntu1","7.34.0-1ubuntu1","7.35.0-1ubuntu1","7.35.0-1ubuntu2","7.35.0-1ubuntu2.1","7.35.0-1ubuntu2.2","7.35.0-1ubuntu2.3","7.35.0-1ubuntu2.5","7.35.0-1ubuntu2.6","7.35.0-1ubuntu2.7","7.35.0-1ubuntu2.8","7.35.0-1ubuntu2.9","7.35.0-1ubuntu2.10","7.35.0-1ubuntu2.11","7.35.0-1ubuntu2.12","7.35.0-1ubuntu2.13","7.35.0-1ubuntu2.14","7.35.0-1ubuntu2.15","7.35.0-1ubuntu2.16","7.35.0-1ubuntu2.17","7.35.0-1ubuntu2.19","7.35.0-1ubuntu2.20","7.35.0-1ubuntu2.20+esm2","7.35.0-1ubuntu2.20+esm3","7.35.0-1ubuntu2.20+esm4","7.35.0-1ubuntu2.20+esm5","7.35.0-1ubuntu2.20+esm6","7.35.0-1ubuntu2.20+esm7","7.35.0-1ubuntu2.20+esm8","7.35.0-1ubuntu2.20+esm9","7.35.0-1ubuntu2.20+esm10","7.35.0-1ubuntu2.20+esm11","7.35.0-1ubuntu2.20+esm12","7.35.0-1ubuntu2.20+esm13","7.35.0-1ubuntu2.20+esm14","7.35.0-1ubuntu2.20+esm15","7.35.0-1ubuntu2.20+esm16","7.35.0-1ubuntu2.20+esm17","7.35.0-1ubuntu2.20+esm18","7.35.0-1ubuntu2.20+esm19"],"ecosystem_specific":{"binaries":[{"binary_name":"curl","binary_version":"7.35.0-1ubuntu2.20+esm19"},{"binary_name":"libcurl3","binary_version":"7.35.0-1ubuntu2.20+esm19"},{"binary_name":"libcurl3-gnutls","binary_version":"7.35.0-1ubuntu2.20+esm19"},{"binary_name":"libcurl3-nss","binary_version":"7.35.0-1ubuntu2.20+esm19"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-6253.json"}},{"package":{"name":"curl","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/curl?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.43.0-1ubuntu2","7.45.0-1ubuntu1","7.46.0-1ubuntu1","7.47.0-1ubuntu1","7.47.0-1ubuntu2","7.47.0-1ubuntu2.1","7.47.0-1ubuntu2.2","7.47.0-1ubuntu2.3","7.47.0-1ubuntu2.4","7.47.0-1ubuntu2.5","7.47.0-1ubuntu2.6","7.47.0-1ubuntu2.7","7.47.0-1ubuntu2.8","7.47.0-1ubuntu2.9","7.47.0-1ubuntu2.11","7.47.0-1ubuntu2.12","7.47.0-1ubuntu2.13","7.47.0-1ubuntu2.14","7.47.0-1ubuntu2.15","7.47.0-1ubuntu2.16","7.47.0-1ubuntu2.18","7.47.0-1ubuntu2.19","7.47.0-1ubuntu2.19+esm1","7.47.0-1ubuntu2.19+esm2","7.47.0-1ubuntu2.19+esm3","7.47.0-1ubuntu2.19+esm4","7.47.0-1ubuntu2.19+esm5","7.47.0-1ubuntu2.19+esm6","7.47.0-1ubuntu2.19+esm7","7.47.0-1ubuntu2.19+esm8","7.47.0-1ubuntu2.19+esm9","7.47.0-1ubuntu2.19+esm10","7.47.0-1ubuntu2.19+esm11","7.47.0-1ubuntu2.19+esm12","7.47.0-1ubuntu2.19+esm13","7.47.0-1ubuntu2.19+esm15"],"ecosystem_specific":{"binaries":[{"binary_name":"curl","binary_version":"7.47.0-1ubuntu2.19+esm15"},{"binary_name":"libcurl3","binary_version":"7.47.0-1ubuntu2.19+esm15"},{"binary_name":"libcurl3-gnutls","binary_version":"7.47.0-1ubuntu2.19+esm15"},{"binary_name":"libcurl3-nss","binary_version":"7.47.0-1ubuntu2.19+esm15"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-6253.json"}},{"package":{"name":"curl","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/curl?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.55.1-1ubuntu2","7.55.1-1ubuntu2.1","7.57.0-1ubuntu1","7.58.0-2ubuntu1","7.58.0-2ubuntu2","7.58.0-2ubuntu3","7.58.0-2ubuntu3.1","7.58.0-2ubuntu3.2","7.58.0-2ubuntu3.3","7.58.0-2ubuntu3.5","7.58.0-2ubuntu3.6","7.58.0-2ubuntu3.7","7.58.0-2ubuntu3.8","7.58.0-2ubuntu3.9","7.58.0-2ubuntu3.10","7.58.0-2ubuntu3.12","7.58.0-2ubuntu3.13","7.58.0-2ubuntu3.14","7.58.0-2ubuntu3.15","7.58.0-2ubuntu3.16","7.58.0-2ubuntu3.17","7.58.0-2ubuntu3.18","7.58.0-2ubuntu3.19","7.58.0-2ubuntu3.20","7.58.0-2ubuntu3.21","7.58.0-2ubuntu3.22","7.58.0-2ubuntu3.23","7.58.0-2ubuntu3.24","7.58.0-2ubuntu3.24+esm1","7.58.0-2ubuntu3.24+esm2","7.58.0-2ubuntu3.24+esm3","7.58.0-2ubuntu3.24+esm4","7.58.0-2ubuntu3.24+esm5","7.58.0-2ubuntu3.24+esm7","7.58.0-2ubuntu3.24+esm8"],"ecosystem_specific":{"binaries":[{"binary_name":"curl","binary_version":"7.58.0-2ubuntu3.24+esm8"},{"binary_name":"libcurl3-gnutls","binary_version":"7.58.0-2ubuntu3.24+esm8"},{"binary_name":"libcurl3-nss","binary_version":"7.58.0-2ubuntu3.24+esm8"},{"binary_name":"libcurl4","binary_version":"7.58.0-2ubuntu3.24+esm8"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-6253.json"}},{"package":{"name":"curl","ecosystem":"Ubuntu:Pro:20.04: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