{"api_version":"1","generated_at":"2026-08-22T21:53:00+00:00","cve":"CVE-2026-75870","urls":{"html":"https://cve.report/CVE-2026-75870","api":"https://cve.report/api/cve/CVE-2026-75870.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-75870","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-75870"},"summary":{"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.","state":"PUBLISHED","assigner":"CPANSec","published_at":"2026-08-22 14:16:33","updated_at":"2026-08-22 19:16:20"},"problem_types":["CWE-1394","CWE-1394 CWE-1394 Use of Default Cryptographic Key"],"metrics":[],"references":[{"url":"https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h","name":"https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h","refsource":"9b29abf9-4ab0-4765-b253-1875cd9b441e","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://metacpan.org/release/LNATION/Punk-0.18/source/Changes","name":"https://metacpan.org/release/LNATION/Punk-0.18/source/Changes","refsource":"9b29abf9-4ab0-4765-b253-1875cd9b441e","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"http://www.openwall.com/lists/oss-security/2026/08/22/5","name":"http://www.openwall.com/lists/oss-security/2026/08/22/5","refsource":"af854a3a-2127-422b-91ae-364da2661108","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm","name":"https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm","refsource":"9b29abf9-4ab0-4765-b253-1875cd9b441e","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-75870","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-75870","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[],"timeline":[],"solutions":[{"source":"CNA","title":"","value":"Upgrade to Punk 0.18 or later.","time":"","lang":"en"}],"workarounds":[{"source":"CNA","title":"","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.","time":"","lang":"en"}],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"providerMetadata":{"dateUpdated":"2026-08-22T19:07:10.053Z","orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE"},"references":[{"url":"http://www.openwall.com/lists/oss-security/2026/08/22/5"}],"title":"CVE Program Container"}],"cna":{"affected":[{"collectionURL":"https://cpan.org/modules","defaultStatus":"unaffected","modules":["Punk"],"packageName":"Punk","packageURL":"pkg:cpan/Punk","programFiles":["xs/app.xs","include/punk/punk_session.h"],"programRoutines":[{"name":"Punk::App::session"},{"name":"ps_load"},{"name":"ps_writeback"}],"versions":[{"lessThan":"0.18","status":"affected","version":"0","versionType":"custom"}]}],"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."}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1394","description":"CWE-1394 Use of Default Cryptographic Key","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-08-22T13:35:58.346Z","orgId":"9b29abf9-4ab0-4765-b253-1875cd9b441e","shortName":"CPANSec"},"references":[{"tags":["technical-description"],"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":["release-notes"],"url":"https://metacpan.org/release/LNATION/Punk-0.18/source/Changes"}],"solutions":[{"lang":"en","value":"Upgrade to Punk 0.18 or later."}],"source":{"discovery":"UNKNOWN"},"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","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"}}},"cveMetadata":{"assignerOrgId":"9b29abf9-4ab0-4765-b253-1875cd9b441e","assignerShortName":"CPANSec","cveId":"CVE-2026-75870","datePublished":"2026-08-22T13:35:58.346Z","dateReserved":"2026-08-18T11:59:49.642Z","dateUpdated":"2026-08-22T19:07:10.053Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-22 14:16:33","lastModifiedDate":"2026-08-22 19:16:20","problem_types":["CWE-1394","CWE-1394 CWE-1394 Use of Default Cryptographic Key"],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"75870","Ordinal":"1","Title":"Punk versions before 0.18 for Perl allow session cookie forgery ","CVE":"CVE-2026-75870","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"75870","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"Punk versions before 0.18 for Perl allow session cookie forgery "}]}}}