{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-56390", "assignerOrgId": "4bb8329e-dd38-46c1-aafb-9bf32bcb93c6", "state": "PUBLISHED", "assignerShortName": "CERT-PL", "dateReserved": "2026-06-21T07:15:13.879Z", "datePublished": "2026-07-29T09:40:03.213Z", "dateUpdated": "2026-07-29T09:40:03.213Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "4bb8329e-dd38-46c1-aafb-9bf32bcb93c6", "shortName": "CERT-PL", "dateUpdated": "2026-07-29T09:40:03.213Z"}, "title": "Arbitrary Output Location Change in GNU Bison", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-73", "description": "CWE-73 External Control of File Name or Path", "type": "CWE"}]}], "affected": [{"vendor": "GNU", "product": "Bison", "repo": "https://cgit.git.savannah.gnu.org/cgit/bison.git/", "versions": [{"status": "affected", "version": "3.8.2", "versionType": "semver"}], "defaultStatus": "unknown"}], "descriptions": [{"lang": "en", "value": "GNU Bison improperly handles grammar\u2011defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller\u2011supplied 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\u00a08d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested\u00a0and confirmed as vulnerable, other versions were not tested but might also be vulnerable.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "GNU Bison improperly handles grammar\u2011defined 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\u2011supplied 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>"}]}], "tags": ["x_open-source"], "references": [{"url": "https://cert.pl/en/posts/2026/07/CVE-2026-56389", "tags": ["third-party-advisory"]}, {"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", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "subIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "MEDIUM", "baseScore": 4.6, "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"}}], "credits": [{"lang": "en", "value": "Micha\u0142 Majchrowicz (AFINE Team)", "type": "finder"}, {"lang": "en", "value": "Marcin Wyczechowski (AFINE Team)", "type": "finder"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

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