{"id":"CVE-2021-23351","aliases":["GHSA-fqh4-rh59-xhvf","SNYK-GOLANG-GITHUBCOMPIRESGOPROXYPROTO-1081577"],"title":"github.com/pires/go-proxyproto denial of service vulnerability","summary":"github.com/pires/go-proxyproto denial of service vulnerability","severity":"medium","cvss":4.9,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H","vendor":"pires","product":"github.com/pires/go-proxyproto","ecosystem":"go","affected":["github.com/pires/go-proxyproto < 0.5.0"],"patched":["github.com/pires/go-proxyproto 0.5.0"],"published":"2021-05-18","updated":"2026-07-08","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-fqh4-rh59-xhvf","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-23351"},{"url":"https://github.com/pires/go-proxyproto/issues/69"},{"url":"https://github.com/pires/go-proxyproto/pull/71"},{"url":"https://github.com/pires/go-proxyproto/commit/7f48261db810703d173f27f3309a808cc2b49b8b"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4BNVGJMVI3ZTZ675EFPUHPGXCKCGSX46"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/C36IBVOZXRTWM7MGTRUTOM56P5RR74VU"},{"url":"https://snyk.io/vuln/SNYK-GOLANG-GITHUBCOMPIRESGOPROXYPROTO-1081577"}],"tags":["osv","go"],"epss":0.01871,"epssPercentile":0.78462,"ingestedAt":"2026-07-09T18:56:36.354Z","slug":"CVE-2021-23351","body":"## Overview\n\nThe package `github.com/pires/go-proxyproto` before 0.5.0 are vulnerable to Denial of Service (DoS) via the `parseVersion1()` function. The reader in this package is a default `bufio.Reader` wrapping a `net.Conn`. It will read from the connection until it finds a newline. Since no limits are implemented in the code, a deliberately malformed V1 header could be used to exhaust memory in a server process using this code - and create a DoS. This can be exploited by sending a stream starting with PROXY and continuing to send data (which does not contain a newline) until the target stops acknowledging. The risk here is small, because only trusted sources should be allowed to send proxy protocol headers.\n\n## Affected packages\n\n- `github.com/pires/go-proxyproto < 0.5.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/pires/go-proxyproto 0.5.0`","depth":"sunlit","depthScore":27,"depthScoreParts":{"impact":27,"likelihood":0.4,"exploitation":0,"ransomware":0},"changes":[]}