{"schemaVersion":3,"id":"CVE-2026-53583","aliases":["UBUNTU-CVE-2026-53583","USN-8907-1","DEBIAN-CVE-2026-53583"],"status":"published","duplicateOf":null,"title":null,"description":"libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. This issue is fixed in versions 1.8.6 and 1.9.5.","dates":{"published":"2026-08-20T18:39:03.676Z","modified":"2026-08-20T19:04:42.247Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.5,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":10,"impact":4.2,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":10,"impact":4.2,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00238,"percentile":0.14029,"severity":"low","asOf":"2026-10-22T00:00:00.000Z","change":{"pp":0.04600000000000001,"baselineDate":"2026-09-22T00:00:00.000Z","baselineScore":0.00192},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-22T00:00:00.000Z","score":0.00238,"percentile":0.14029}],"last30":[{"date":"2026-09-22T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00192,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00238,"percentile":null},{"date":"2026-10-22T00:00:00.000Z","score":0.00238,"percentile":0.14029}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-295","name":"Improper Certificate Validation","description":"The product does not validate, or incorrectly validates, a certificate.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/295.html"},{"id":"CWE-297","name":"Improper Validation of Certificate with Host Mismatch","description":"The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.","type":"weakness","status":"Incomplete","abstraction":"Variant","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/297.html"}],"affected":[{"vendor":"debian","product":"libgit2","name":"libgit2","label":"libgit2","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/libgit2","purlType":"deb","versions":[{"text":"< 1.9.0+ds-2+deb13u1","noFixRecorded":false,"fixedIn":null},{"text":"< 1.9.6+ds-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.9.0+ds-2+deb13u1 | < 1.9.6+ds-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"libgit2","name":"libgit2","label":"libgit2","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/libgit2","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 1.7.2+ds-1ubuntu3.3","noFixRecorded":false,"fixedIn":null},{"text":"< 1.9.1+ds-1ubuntu1.3","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 1.7.2+ds-1ubuntu3.3 | < 1.9.1+ds-1ubuntu1.3","eol":null,"hubHref":null},{"vendor":"libgit2","product":"libgit2","name":"libgit2","label":"libgit2","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 1.8.6","noFixRecorded":false,"fixedIn":null},{"text":"≥ 1.9.0, < 1.9.5","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.8.6 | ≥ 1.9.0, < 1.9.5","eol":null,"hubHref":"/vendor/libgit2/libgit2"}],"affectedCount":3,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/libgit2/libgit2/security/advisories/GHSA-h7gc-w2gg-p9xp","label":"github.com/libgit2/libgit2/security/advisories/GHSA-h7gc-w2gg-p9xp","hostname":"github.com","tags":["X Refsource CONFIRM","REPORT"]},{"url":"https://github.com/libgit2/libgit2/commit/647dcb432980b84ede4cb5a008bbd1ccb4ead03d","label":"github.com/libgit2/libgit2/commit/647dcb432980b84ede4cb5a008bbd1ccb4ead03d","hostname":"github.com","tags":["X Refsource MISC"]},{"url":"https://github.com/libgit2/libgit2/commit/c2aa35409ee0e6515df64da49750f13a0a42c47f","label":"github.com/libgit2/libgit2/commit/c2aa35409ee0e6515df64da49750f13a0a42c47f","hostname":"github.com","tags":["X Refsource MISC"]},{"url":"https://github.com/libgit2/libgit2/commit/ef086bc3e4eedf62be38a910381aae24d49871ff","label":"github.com/libgit2/libgit2/commit/ef086bc3e4eedf62be38a910381aae24d49871ff","hostname":"github.com","tags":["X Refsource MISC"]},{"url":"https://github.com/libgit2/libgit2/releases/tag/v1.8.6","label":"github.com/libgit2/libgit2/releases/tag/v1.8.6","hostname":"github.com","tags":["X Refsource MISC"]},{"url":"https://github.com/libgit2/libgit2/releases/tag/v1.9.5","label":"github.com/libgit2/libgit2/releases/tag/v1.9.5","hostname":"github.com","tags":["X Refsource MISC"]},{"url":"https://ubuntu.com/security/CVE-2026-53583","label":"ubuntu.com/security/CVE-2026-53583","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-53583","label":"www.cve.org/CVERecord?id=CVE-2026-53583","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://ubuntu.com/security/notices/USN-8907-1","label":"ubuntu.com/security/notices/USN-8907-1","hostname":"ubuntu.com","tags":["Advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-53583","label":"security-tracker.debian.org/tracker/CVE-2026-53583","hostname":"security-tracker.debian.org","tags":["Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53583","label":"nvd.nist.gov/vuln/detail/CVE-2026-53583","hostname":"nvd.nist.gov","tags":["Oval","Advisory"]}],"lineage":{"upstream":[],"downstream":["OPENSUSE-SU-2026:11315-1","RHSA-2026:59361"],"duplicates":[],"related":["OPENSUSE-SU-2026:11315-1"]},"timeline":[{"kind":"published","date":"2026-08-20T18:39:03.676Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-08-20T19:04:42.247Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":26,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-22T16:10:03.914Z","stale":false,"partial":false}}