{"id":"CVE-2026-75870","state":"PUBLISHED","title":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret","description":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.\n\nThe session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key.\n\nAn attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected.","publishedAt":"2026-08-22T13:35:58.346Z","updatedAt":"2026-08-25T19:28:36.443Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"CISA-ADP"},"assigner":"CPANSec","products":["Punk"],"affected":[{"packageName":"Punk","packageURL":"pkg:cpan/Punk","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"0.18","versionType":"custom"}],"collectionURL":"https://cpan.org/modules","modules":["Punk"],"programFiles":["xs/app.xs","include/punk/punk_session.h"],"programRoutines":[{"name":"Punk::App::session"},{"name":"ps_load"},{"name":"ps_writeback"}]}],"references":["https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h","https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm","https://metacpan.org/release/LNATION/Punk-0.18/source/Changes","http://www.openwall.com/lists/oss-security/2026/08/22/5"],"weaknesses":["CWE-1394"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/75xxx/CVE-2026-75870.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-75870","state":"PUBLISHED","datePublished":"2026-08-22T13:35:58.346Z","dateUpdated":"2026-08-25T19:28:36.443Z","assignerShortName":"CPANSec","assignerOrgId":"9b29abf9-4ab0-4765-b253-1875cd9b441e","dateReserved":"2026-08-18T11:59:49.642Z"},"containers":{"cna":{"title":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret","descriptions":[{"lang":"en","value":"Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.\n\nThe session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key.\n\nAn attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected."}],"affected":[{"packageName":"Punk","packageURL":"pkg:cpan/Punk","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"0.18","versionType":"custom"}],"collectionURL":"https://cpan.org/modules","modules":["Punk"],"programFiles":["xs/app.xs","include/punk/punk_session.h"],"programRoutines":[{"name":"Punk::App::session"},{"name":"ps_load"},{"name":"ps_writeback"}]}],"references":[{"url":"https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h","tags":["technical-description"]},{"url":"https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm","tags":["technical-description"]},{"url":"https://metacpan.org/release/LNATION/Punk-0.18/source/Changes","tags":["release-notes"]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1394","description":"CWE-1394 Use of Default Cryptographic Key","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"CPANSec","orgId":"9b29abf9-4ab0-4765-b253-1875cd9b441e","dateUpdated":"2026-08-22T13:35:58.346Z"},"solutions":[{"lang":"en","value":"Upgrade to Punk 0.18 or later."}],"source":{"discovery":"UNKNOWN"},"workarounds":[{"lang":"en","value":"For deployments that cannot upgrade to 0.18, declare the session keyword with a non-empty secret. The secret keyword fails closed, so sourcing the key through it turns a missing configuration path or an unset environment variable into a startup error."}],"x_generator":{"engine":"cpansec-cna-tool 0.1"}},"adp":[{"title":"CVE Program Container","references":[{"url":"http://www.openwall.com/lists/oss-security/2026/08/22/5"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2026-08-22T19:07:10.053Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":9.1,"attackVector":"NETWORK","baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"NONE","privilegesRequired":"NONE","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"timestamp":"2026-08-25T19:27:34.454527Z","id":"CVE-2026-75870","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-25T19:28:36.443Z"}}]}}}