{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-23409", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:46.013Z", "datePublished": "2026-04-01T08:36:38.516Z", "dateUpdated": "2026-04-01T08:36:38.516Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-04-01T08:36:38.516Z"}, "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["security/apparmor/include/match.h", "security/apparmor/match.c"], "versions": [{"version": "031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3", "lessThan": "f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a", "status": "affected", "versionType": "git"}, {"version": "031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3", "lessThan": "34fc60b125ed1d4eb002c76b0664bf0619492167", "status": "affected", "versionType": "git"}, {"version": "031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3", "lessThan": "623a9d211bbbb031bb1cbdb38b23487648167f8a", "status": "affected", "versionType": "git"}, {"version": "031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3", "lessThan": "1ff4857fac56ac5a90ee63b24db05fa5e91a45aa", "status": "affected", "versionType": "git"}, {"version": "031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3", "lessThan": "39440b137546a3aa383cfdabc605fb73811b6093", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["security/apparmor/include/match.h", "security/apparmor/match.c"], "versions": [{"version": "4.17", "status": "affected"}, {"version": "0", "lessThan": "4.17", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.130", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.77", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.18", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.8", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0-rc4", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.6.130"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.12.77"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.18.18"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.19.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "7.0-rc4"}]}]}], "references": [{"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"}}}}

{}

{"cveTags": [], "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."}], "id": "CVE-2026-23409", "lastModified": "2026-04-01T14:23:37.727", "metrics": {}, "published": "2026-04-01T09:16:16.913", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1ff4857fac56ac5a90ee63b24db05fa5e91a45aa"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/34fc60b125ed1d4eb002c76b0664bf0619492167"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/39440b137546a3aa383cfdabc605fb73811b6093"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/623a9d211bbbb031bb1cbdb38b23487648167f8a"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"bugzilla": {"description": "kernel: apparmor: fix differential encoding verification", "id": "2453804", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2453804"}, "csaw": false, "cwe": "CWE-372", "details": ["A flaw was found in AppArmor, a security module in the Linux kernel. This vulnerability occurs due to incorrect verification of differential encoding chains, which are designed to prevent malicious loops. An attacker could exploit this flaw by crafting a specially designed differential encoding chain, causing the system to misinterpret it as already verified. This could lead to a bypass of security policies and potentially result in unexpected system behavior or a denial of service."], "name": "CVE-2026-23409", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-23409\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23409\nhttps://lore.kernel.org/linux-cve-announce/2026040113-CVE-2026-23409-ae18@gregkh/T"]}

{}