{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-74544", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.914Z", "datePublished": "2026-08-15T12:27:53.941Z", "dateUpdated": "2026-08-17T05:48:31.015Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:48:31.015Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: validate offshift to prevent shift-out-of-bounds\n\nu32_change() copies the user-provided tc_u32_sel.offshift (unsigned char,\n0-255) into the kernel knode object without bounds validation. When a\npacket later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates\n`ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit\nvalue promoted to a 32-bit int. Any offshift >= 32 is undefined behavior\nper C11 6.5.7p3, triggerable by an unprivileged user via user/network\nnamespaces.\n\nUBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43\nshift exponent 32 is too large for 32-bit type int\n\nFix this by rejecting offshift >= 16 during filter creation in\nu32_change()."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The bug is configured through RTM_NEWTFILTER rtnetlink (tc filter add) in u32_change(); per kernel CNA guidance, tc/qdisc/netlink classifier setup is Local even though subsequent packets invoke u32_classify() on ingress/egress paths.\nAC:L - The attacker fully controls offshift (32-255), TC_U32_VAROFFSET selector flags, and matching packet bytes when installing the filter and sending traffic through the attached qdisc; no race or external victim state is required.\nPR:L - Creating u32 filters requires CAP_NET_ADMIN, which an unprivileged local user obtains in a user/network namespace via unshare -Urn; rtnetlink enforces netlink_net_capable() against that namespace's user_ns, not only init-root.\nUI:N - The attacker installs the malicious u32 filter and injects triggering packets themselves within their namespace; no separate victim action (opening files, mounting media, clicking links) is needed.\nS:U - Corrupted classifier offset arithmetic and any resulting kernel crash stay within the host kernel's security authority; this is standard local kernel compromise, not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - Undefined-behavior right-shift (offshift>=32) on packet-derived values corrupts variable offset math in u32_classify(), driving attacker-influenced skb_header_pointer reads at unintended offsets; per CNA guidance, exploitable kernel memory-unsafe operations warrant High confidentiality impact.\nI:H - Invalid shift results corrupt off2 and unsigned off accumulation in the classifier hot path, derailing cls_u32 control flow; C11 undefined behavior in kernel packet classification is exploitable for integrity compromise and potential code execution per CNA memory-corruption guidance.\nA:H - Hitting u32_classify() with offshift>=32 provokes documented UBSAN shift-out-of-bounds at cls_u32.c:236; undefined shifts can also trigger kernel oops/panic during packet classification, satisfying CNA guidance that kernel crashes are High availability impact."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/cls_u32.c"], "versions": [{"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "313cb9ffc4101a885d791facf4b5ea3d5e06144d", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "aef96eead2860cbfa371e4471d4f04412213b958", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/cls_u32.c"], "versions": [{"version": "2.6.12", "status": "affected"}, {"version": "0", "lessThan": "2.6.12", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.8", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2", "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": "2.6.12", "versionEndExcluding": "7.1.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "7.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/313cb9ffc4101a885d791facf4b5ea3d5e06144d"}, {"url": "https://git.kernel.org/stable/c/aef96eead2860cbfa371e4471d4f04412213b958"}], "title": "net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/sched/cls_u32.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "313cb9ffc4101a885d791facf4b5ea3d5e06144d", "status": "affected", "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "versionType": "git"}, {"lessThan": "aef96eead2860cbfa371e4471d4f04412213b958", "status": "affected", "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["net/sched/cls_u32.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "2.6.12"}, {"lessThan": "2.6.12", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.8", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: validate offshift to prevent shift-out-of-bounds\n\nu32_change() copies the user-provided tc_u32_sel.offshift (unsigned char,\n0-255) into the kernel knode object without bounds validation. When a\npacket later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates\n`ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit\nvalue promoted to a 32-bit int. Any offshift >= 32 is undefined behavior\nper C11 6.5.7p3, triggerable by an unprivileged user via user/network\nnamespaces.\n\nUBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43\nshift exponent 32 is too large for 32-bit type int\n\nFix this by rejecting offshift >= 16 during filter creation in\nu32_change()."}], "id": "CVE-2026-74544", "lastModified": "2026-08-17T06:19:51.597", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-08-15T13:17:59.753", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/313cb9ffc4101a885d791facf4b5ea3d5e06144d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/aef96eead2860cbfa371e4471d4f04412213b958"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds", "id": "2517014", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2517014"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-1335", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nnet/sched: cls_u32: validate offshift to prevent shift-out-of-bounds\nu32_change() copies the user-provided tc_u32_sel.offshift (unsigned char,\n0-255) into the kernel knode object without bounds validation. When a\npacket later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates\n`ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit\nvalue promoted to a 32-bit int. Any offshift >= 32 is undefined behavior\nper C11 6.5.7p3, triggerable by an unprivileged user via user/network\nnamespaces.\nUBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43\nshift exponent 32 is too large for 32-bit type int\nFix this by rejecting offshift >= 16 during filter creation in\nu32_change().", "A flaw was found in the Linux kernel's `cls_u32` module. An unprivileged user, through user or network namespaces, could provide a specially crafted `offshift` value that is not properly validated. This improper validation leads to a shift-out-of-bounds condition, resulting in undefined behavior and potentially causing a denial of service or system instability."], "name": "CVE-2026-74544", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-08-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-74544\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-74544\nhttps://lore.kernel.org/linux-cve-announce/2026081549-CVE-2026-74544-2dcd@gregkh/T"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,313cb9ffc4101a885d791facf4b5ea3d5e06144d)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,aef96eead2860cbfa371e4471d4f04412213b958)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.6.12"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,2.6.12)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.1.8,7.2.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.2-rc6,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-08-15T15:15:03.212472+00:00", "updated": "2026-08-21T23:15:05.353298+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}