{"api_version":"1","generated_at":"2026-08-02T02:56:18+00:00","cve":"CVE-2026-56390","urls":{"html":"https://cve.report/CVE-2026-56390","api":"https://cve.report/api/cve/CVE-2026-56390.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-56390","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-56390"},"summary":{"title":"Arbitrary Output Location Change in GNU Bison","description":"GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller‑supplied output options. \nWhen processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process.\n\nMaintainers of this project were notified about this vulnerability, and fixed the issue in commit 8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable.","state":"PUBLISHED","assigner":"CERT-PL","published_at":"2026-07-29 11:16:49","updated_at":"2026-07-30 16:28:33"},"problem_types":["CWE-73","CWE-73 CWE-73 External Control of File Name or Path"],"metrics":[{"version":"4.0","source":"cvd@cert.pl","type":"Secondary","score":"4.6","severity":"MEDIUM","vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","data":{"version":"4.0","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","baseScore":4.6,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}},{"version":"4.0","source":"CNA","type":"CVSS","score":"4.6","severity":"MEDIUM","vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N","data":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":4.6,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","userInteraction":"ACTIVE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnerabilityResponseEffort":"NOT_DEFINED"}}],"references":[{"url":"https://cgit.git.savannah.gnu.org/cgit/bison.git/","name":"https://cgit.git.savannah.gnu.org/cgit/bison.git/","refsource":"cvd@cert.pl","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://cert.pl/en/posts/2026/07/CVE-2026-56389","name":"https://cert.pl/en/posts/2026/07/CVE-2026-56389","refsource":"cvd@cert.pl","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a448c925513742d4efcf0","name":"https://cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a448c925513742d4efcf0","refsource":"cvd@cert.pl","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-56390","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56390","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"GNU","product":"Bison","version":"affected 3.8.2 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Michał Majchrowicz (AFINE Team)","lang":"en"},{"source":"CNA","value":"Marcin Wyczechowski (AFINE Team)","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"56390","cve":"CVE-2026-56390","epss":"0.001330000","percentile":"0.032360000","score_date":"2026-08-01","updated_at":"2026-08-02 00:11:13"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-56390","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-07-29T12:14:42.510020Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-07-29T12:15:19.804Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unknown","product":"Bison","repo":"https://cgit.git.savannah.gnu.org/cgit/bison.git/","vendor":"GNU","versions":[{"status":"affected","version":"3.8.2","versionType":"semver"}]}],"credits":[{"lang":"en","type":"finder","value":"Michał Majchrowicz (AFINE Team)"},{"lang":"en","type":"finder","value":"Marcin Wyczechowski (AFINE Team)"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as <i>%output</i> and <i>%header</i> allow specifying file paths, which are accepted without restriction and override caller‑supplied output options. <br>When processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process.<br><br>Maintainers of this project were notified about this vulnerability, and fixed the issue in commit&nbsp;8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested&nbsp;and confirmed as vulnerable, other versions were not tested but might also be vulnerable.<br>"}],"value":"GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller‑supplied output options. \nWhen processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process.\n\nMaintainers of this project were notified about this vulnerability, and fixed the issue in commit 8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable."}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":4.6,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","userInteraction":"ACTIVE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-73","description":"CWE-73 External Control of File Name or Path","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-07-29T09:40:03.213Z","orgId":"4bb8329e-dd38-46c1-aafb-9bf32bcb93c6","shortName":"CERT-PL"},"references":[{"tags":["third-party-advisory"],"url":"https://cert.pl/en/posts/2026/07/CVE-2026-56389"},{"tags":["patch"],"url":"https://cgit.git.savannah.gnu.org/cgit/bison.git/"},{"tags":["patch"],"url":"https://cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a448c925513742d4efcf0"}],"source":{"discovery":"UNKNOWN"},"tags":["x_open-source"],"title":"Arbitrary Output Location Change in GNU Bison","x_generator":{"engine":"Vulnogram 0.2.0"}}},"cveMetadata":{"assignerOrgId":"4bb8329e-dd38-46c1-aafb-9bf32bcb93c6","assignerShortName":"CERT-PL","cveId":"CVE-2026-56390","datePublished":"2026-07-29T09:40:03.213Z","dateReserved":"2026-06-21T07:15:13.879Z","dateUpdated":"2026-07-29T12:15:19.804Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-29 11:16:49","lastModifiedDate":"2026-07-30 16:28:33","problem_types":["CWE-73","CWE-73 CWE-73 External Control of File Name or Path"],"metrics":{"cvssMetricV40":[{"source":"cvd@cert.pl","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","baseScore":4.6,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-07-29T12:14:42.510020Z","id":"CVE-2026-56390","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"56390","Ordinal":"1","Title":"Arbitrary Output Location Change in GNU Bison","CVE":"CVE-2026-56390","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"56390","Ordinal":"1","NoteData":"GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller‑supplied output options. \nWhen processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process.\n\nMaintainers of this project were notified about this vulnerability, and fixed the issue in commit 8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable.","Type":"Description","Title":"Arbitrary Output Location Change in GNU Bison"}]}}}