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vulnerability has been resolved:\n\nxfrm: clear trailing padding in build_polexpire()\n\nbuild_expire() clears the trailing padding bytes of struct\nxfrm_user_expire after setting the hard field via memset_after(),\nbut the analogous function build_polexpire() does not do this for\nstruct xfrm_user_polexpire.\n\nThe padding bytes after the __u8 hard field are left\nuninitialized from the heap allocation, and are then sent to\nuserspace via netlink multicast to XFRMNLGRP_EXPIRE listeners,\nleaking kernel heap memory contents.\n\nAdd the missing memset_after() call, matching build_expire()."}], "id": "CVE-2026-31664", "lastModified": "2026-04-27T19:59:44.497", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2026-04-24T15:16:46.043", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/71a98248c63c535eaa4d4c22f099b68d902006d0"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ac6985903db047eaff54db929e4bf6b06782788e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c221ed63a2769a0af8bd849dfe25740048f34ef4"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e1af65c669ebb1666c54576614c01a7f9ffcfff6"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/eda30846ea54f8ed218468e5480c8305ca645e37"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: xfrm: clear trailing padding in build_polexpire()", "id": "2461482", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461482"}, "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-908", "details": ["A flaw was found in the Linux kernel's xfrm subsystem. This vulnerability arises because the `build_polexpire()` function does not clear trailing padding bytes within the `xfrm_user_polexpire` structure. Consequently, these uninitialized padding bytes, which contain kernel heap memory contents, are sent to userspace via netlink multicast. A local attacker could exploit this to disclose potentially sensitive information from kernel memory."], "name": "CVE-2026-31664", "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": "2026-04-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31664\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31664\nhttps://lore.kernel.org/linux-cve-announce/2026042405-CVE-2026-31664-d315@gregkh/T"], "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,ac6985903db047eaff54db929e4bf6b06782788e)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,c221ed63a2769a0af8bd849dfe25740048f34ef4)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,eda30846ea54f8ed218468e5480c8305ca645e37)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,b1dfd6b27df35ef4f87825aa5f607378d23ff0f2)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,e1af65c669ebb1666c54576614c01a7f9ffcfff6)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,71a98248c63c535eaa4d4c22f099b68d902006d0)"}}], "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": "[6.1.169,6.2.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.6.135,6.7.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.12.82,6.13.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.23,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.19.13,6.20.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.0,*]"}}], "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"}], "analysis": {"en": {"generated_at": "2026-04-28T20:02:43.022903+00:00", "value": {"mitigation_remediation": ["Apply a kernel update that includes the patch from commit 71a98248, which adds the missing memset_after() call in build_polexpire().", "If an immediate kernel upgrade is not possible, restrict netlink access to the XFRMNLGRP_EXPIRE multicast group by configuring firewall rules or application-level permissions, thus preventing unauthorized processes from receiving the leaked kernel data.", "Implement monitoring of netlink traffic or kernel audit rules to detect unexpected XFRMNLGRP_EXPIRE messages, helping to identify attempted exploitation and verify that the padding is cleared in memory."], "summary": {"action": "Patch kernel", "impact": "Information disclosure"}, "threat_synthesis": {"affected_systems": "The vulnerability exists in Linux kernel versions that have not yet incorporated the patch for build_polexpire(). Specifically, release candidates of the 2.6.12 series (rc1 through rc5) and of the 7.0 series (rc1 through rc7) contain the vulnerable code. The fix was merged into mainline Linux (commit 71a98248) and is included in all kernels released after that commit.", "description_and_impact": "The flaw resides in the xfrm kernel module\u2019s build_polexpire() function, which fails to clear the padding bytes that follow the hard field in a struct xfrm_user_polexpire. Because these bytes are left uninitialized, they are copied from kernel heap memory and then sent to userspace via netlink multicast when a XFRMNLGRP_EXPIRE listener receives the message. The result is an information disclosure of arbitrary kernel heap contents to any process that can receive the multicast packets. This type of defect corresponds to CWE\u2011908. Based on the description, the attack vector appears to require the ability to subscribe to the XFRMNLGRP_EXPIRE netlink group, which generally means local or privileged access.", "risk_and_exploitability": "The CVSS base score of 5.5 indicates medium severity. The EPSS score of less than 1% suggests that the likelihood of exploitation in the wild is low. The vulnerability is not listed in the CISA KEV catalog. Exploitation would require an attacker to observe or inject into the XFRMNLGRP_EXPIRE netlink multicast traffic, which typically implies local or privileged user context. Consequently, the overall risk is moderate, but the expected probability of successful exploitation is low."}}}}, "created": "2026-04-27T19:45:11.179515+00:00", "updated": "2026-04-28T20:15:26.793915+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}