{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63952", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.023Z", "datePublished": "2026-07-19T14:55:44.809Z", "dateUpdated": "2026-08-05T12:37:37.398Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:37:37.398Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmemfd: deny writeable mappings when implying SEAL_WRITE\n\nWhen SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the\nimplied seal is set after the check that makes sure the memfd can not have\nany writable mappings. This means one can use SEAL_EXEC to apply\nSEAL_WRITE while having writeable mappings.\n\nThis breaks the contract that SEAL_WRITE provides and can be used by an\nattacker to pass a memfd that appears to be write sealed but can still be\nmodified arbitrarily.\n\nFix this by adding the implied seals before the call for\nmapping_deny_writable() is done." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N", "baseScore": 8.4, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires local syscalls (memfd_create, mmap, fcntl) with no network-facing code path; the vulnerable logic is reached only through the local fcntl(F_ADD_SEALS) interface on a memfd file descriptor.\nAC:L - The attack is a reliable, deterministic syscall sequence (create executable memfd, establish a writable MAP_SHARED mapping, then apply F_SEAL_EXEC) with no race or attacker-uncontrollable conditions.\nPR:L - Any unprivileged local user can invoke memfd_create, mmap, and fcntl without capabilities; these interfaces are available inside unprivileged user namespaces with no real-root requirement.\nUI:N - Exploitation does not require a human victim action; in the highest-impact scenario a sandboxed process programmatically passes the sealed-appearing memfd to a trusting peer via IPC (e.g., SCM_RIGHTS) without user interaction.\nS:C - The bug breaks the memfd seal security contract designed for mutually untrusted parties, allowing a malicious local peer to deceive a separate process that relies on F_SEAL_WRITE immutability, crossing the inter-process trust boundary (sandbox/W^X enforcement).\nC:H - Bypassing write-seal/W^X guarantees enables arbitrary modification of executable memfd contents presented as immutable, which can be leveraged for arbitrary code execution in a trusting victim process and thereby full read of that process's memory.\nI:H - The vulnerability allows arbitrary modification of memory that is advertised as write-sealed (F_SEAL_WRITE), defeating the kernel's immutability guarantee and enabling W^X bypass and code injection into trusted execution contexts.\nA:N - The flaw is a logic error in seal enforcement that does not cause kernel crashes, panics, hangs, or denial of service; exploitation maintains availability while subverting integrity guarantees." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "mm/memfd.c" ], "versions": [ { "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601", "lessThan": "b3f4f82d1315f1439059a83d1c22c51a5b43d99e", "status": "affected", "versionType": "git" }, { "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601", "lessThan": "3be2a24f7f72ad7321ed6ad1715b956a4527bcf4", "status": "affected", "versionType": "git" }, { "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601", "lessThan": "0995d1f79aed8ccbf62056189dd53fd19726ea08", "status": "affected", "versionType": "git" }, { "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601", "lessThan": "555702282d4536a865dfffb1cd4f6028f196e7e8", "status": "affected", "versionType": "git" }, { "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601", "lessThan": "3b041514cb6eae45869b020f743c14d983363222", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "mm/memfd.c" ], "versions": [ { "version": "6.3", "status": "affected" }, { "version": "0", "lessThan": "6.3", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "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": "6.3", "versionEndExcluding": "6.6.143" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e" }, { "url": "https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4" }, { "url": "https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08" }, { "url": "https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8" }, { "url": "https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222" } ], "title": "memfd: deny writeable mappings when implying SEAL_WRITE", "x_generator": { "engine": "bippy-1.2.0" } } } }