{"api_version":"1","generated_at":"2026-04-19T01:13:12+00:00","cve":"CVE-2026-23409","urls":{"html":"https://cve.report/CVE-2026-23409","api":"https://cve.report/api/cve/CVE-2026-23409.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-23409","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-23409"},"summary":{"title":"apparmor: fix differential encoding verification","description":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix differential encoding verification\n\nDifferential encoding allows loops to be created if it is abused. To\nprevent this the unpack should verify that a diff-encode chain\nterminates.\n\nUnfortunately the differential encode verification had two bugs.\n\n1. it conflated states that had gone through check and already been\n   marked, with states that were currently being checked and marked.\n   This means that loops in the current chain being verified are treated\n   as a chain that has already been verified.\n\n2. the order bailout on already checked states compared current chain\n   check iterators j,k instead of using the outer loop iterator i.\n   Meaning a step backwards in states in the current chain verification\n   was being mistaken for moving to an already verified state.\n\nMove to a double mark scheme where already verified states get a\ndifferent mark, than the current chain being kept. This enables us\nto also drop the backwards verification check that was the cause of\nthe second error as any already verified state is already marked.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-01 09:16:16","updated_at":"2026-04-18 09:16:25"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa","name":"https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a","name":"https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a","name":"https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a","name":"https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167","name":"https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84","name":"https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0","name":"https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093","name":"https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-23409","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23409","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 1439150cd3c411228b387ab5efca92199d2a659a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 0fab44285445e9012674396d5c1236a67da518e0 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.169 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.130 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.77 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.18 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.8 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"23409","cve":"CVE-2026-23409","epss":"0.000320000","percentile":"0.090980000","score_date":"2026-04-18","updated_at":"2026-04-19 00:10:43"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["security/apparmor/include/match.h","security/apparmor/match.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"1439150cd3c411228b387ab5efca92199d2a659a","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"0fab44285445e9012674396d5c1236a67da518e0","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"34fc60b125ed1d4eb002c76b0664bf0619492167","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"623a9d211bbbb031bb1cbdb38b23487648167f8a","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"1ff4857fac56ac5a90ee63b24db05fa5e91a45aa","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"},{"lessThan":"39440b137546a3aa383cfdabc605fb73811b6093","status":"affected","version":"031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["security/apparmor/include/match.h","security/apparmor/match.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"4.17"},{"lessThan":"4.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.253","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.203","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.169","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.130","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.77","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.18","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.8","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.253","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.203","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.169","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.130","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.77","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.18","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.8","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"4.17","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix differential encoding verification\n\nDifferential encoding allows loops to be created if it is abused. To\nprevent this the unpack should verify that a diff-encode chain\nterminates.\n\nUnfortunately the differential encode verification had two bugs.\n\n1. it conflated states that had gone through check and already been\n   marked, with states that were currently being checked and marked.\n   This means that loops in the current chain being verified are treated\n   as a chain that has already been verified.\n\n2. the order bailout on already checked states compared current chain\n   check iterators j,k instead of using the outer loop iterator i.\n   Meaning a step backwards in states in the current chain verification\n   was being mistaken for moving to an already verified state.\n\nMove to a double mark scheme where already verified states get a\ndifferent mark, than the current chain being kept. This enables us\nto also drop the backwards verification check that was the cause of\nthe second error as any already verified state is already marked."}],"providerMetadata":{"dateUpdated":"2026-04-18T08:58:44.586Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84"},{"url":"https://git.kernel.org/stable/c/1439150cd3c411228b387ab5efca92199d2a659a"},{"url":"https://git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0"},{"url":"https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a"},{"url":"https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167"},{"url":"https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a"},{"url":"https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa"},{"url":"https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093"}],"title":"apparmor: fix differential encoding verification","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-23409","datePublished":"2026-04-01T08:36:38.516Z","dateReserved":"2026-01-13T15:37:46.013Z","dateUpdated":"2026-04-18T08:58:44.586Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-01 09:16:16","lastModifiedDate":"2026-04-18 09:16:25","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"23409","Ordinal":"1","Title":"apparmor: fix differential encoding verification","CVE":"CVE-2026-23409","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"23409","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix differential encoding verification\n\nDifferential encoding allows loops to be created if it is abused. To\nprevent this the unpack should verify that a diff-encode chain\nterminates.\n\nUnfortunately the differential encode verification had two bugs.\n\n1. it conflated states that had gone through check and already been\n   marked, with states that were currently being checked and marked.\n   This means that loops in the current chain being verified are treated\n   as a chain that has already been verified.\n\n2. the order bailout on already checked states compared current chain\n   check iterators j,k instead of using the outer loop iterator i.\n   Meaning a step backwards in states in the current chain verification\n   was being mistaken for moving to an already verified state.\n\nMove to a double mark scheme where already verified states get a\ndifferent mark, than the current chain being kept. This enables us\nto also drop the backwards verification check that was the cause of\nthe second error as any already verified state is already marked.","Type":"Description","Title":"apparmor: fix differential encoding verification"}]}}}