{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63804", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.013Z", "datePublished": "2026-07-19T12:02:09.111Z", "dateUpdated": "2026-08-17T04:51:09.991Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:51:09.991Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ngfs2: fix use-after-free in gfs2_qd_dealloc\n\ngfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(),\naccesses the superblock object sdp through qd->qd_sbd after freeing qd.\nIt does so to decrement sd_quota_count and wake up sd_kill_wait.\n\nHowever, by the time the RCU callback runs, gfs2_put_super() may have\nalready freed sdp via free_sbd(). This can happen when\ngfs2_quota_cleanup() is called during unmount: it disposes of quota\nobjects via call_rcu() and then waits on sd_kill_wait with a 60-second\ntimeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers\nadditional qd_put() calls that schedule more RCU callbacks after the\nwait completes, gfs2_put_super() will proceed to free the superblock\nwhile RCU callbacks referencing it are still pending.\n\nAdd an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure\nall pending RCU callbacks (including gfs2_qd_dealloc) have completed\nbefore the superblock is freed."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/gfs2/super.c"], "versions": [{"version": "a475c5dd16e57c570113eccba51955b5df8bb052", "lessThan": "4fe388218826df8607ae41a6305df67db08a9093", "status": "affected", "versionType": "git"}, {"version": "a475c5dd16e57c570113eccba51955b5df8bb052", "lessThan": "8745d9f7e1682c39f0a1578895ac74205e2a6757", "status": "affected", "versionType": "git"}, {"version": "a475c5dd16e57c570113eccba51955b5df8bb052", "lessThan": "b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0", "status": "affected", "versionType": "git"}, {"version": "a475c5dd16e57c570113eccba51955b5df8bb052", "lessThan": "9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0", "status": "affected", "versionType": "git"}, {"version": "a475c5dd16e57c570113eccba51955b5df8bb052", "lessThan": "f9c9ec2c319f843b70ecdf939d48b52d189bc081", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/gfs2/super.c"], "versions": [{"version": "6.6", "status": "affected"}, {"version": "0", "lessThan": "6.6", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.144", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.38", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.3", "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": "6.6", "versionEndExcluding": "6.6.144"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.12.95"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.18.38"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.1.3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/4fe388218826df8607ae41a6305df67db08a9093"}, {"url": "https://git.kernel.org/stable/c/8745d9f7e1682c39f0a1578895ac74205e2a6757"}, {"url": "https://git.kernel.org/stable/c/b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0"}, {"url": "https://git.kernel.org/stable/c/9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0"}, {"url": "https://git.kernel.org/stable/c/f9c9ec2c319f843b70ecdf939d48b52d189bc081"}], "title": "gfs2: fix use-after-free in gfs2_qd_dealloc", "x_generator": {"engine": "bippy-1.2.0"}}}}

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This can happen when\ngfs2_quota_cleanup() is called during unmount: it disposes of quota\nobjects via call_rcu() and then waits on sd_kill_wait with a 60-second\ntimeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers\nadditional qd_put() calls that schedule more RCU callbacks after the\nwait completes, gfs2_put_super() will proceed to free the superblock\nwhile RCU callbacks referencing it are still pending.\n\nAdd an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure\nall pending RCU callbacks (including gfs2_qd_dealloc) have completed\nbefore the superblock is freed."}], "id": "CVE-2026-63804", "lastModified": "2026-08-17T05:17:17.033", "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": "nvd@nist.gov", "type": "Primary"}]}, "published": "2026-07-19T12:16:53.120", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4fe388218826df8607ae41a6305df67db08a9093"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8745d9f7e1682c39f0a1578895ac74205e2a6757"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f9c9ec2c319f843b70ecdf939d48b52d189bc081"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: gfs2: fix use-after-free in gfs2_qd_dealloc", "id": "2502203", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2502203"}, "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-825", "details": ["In the Linux kernel, the following vulnerability has been resolved:\ngfs2: fix use-after-free in gfs2_qd_dealloc\ngfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(),\naccesses the superblock object sdp through qd->qd_sbd after freeing qd.\nIt does so to decrement sd_quota_count and wake up sd_kill_wait.\nHowever, by the time the RCU callback runs, gfs2_put_super() may have\nalready freed sdp via free_sbd(). This can happen when\ngfs2_quota_cleanup() is called during unmount: it disposes of quota\nobjects via call_rcu() and then waits on sd_kill_wait with a 60-second\ntimeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers\nadditional qd_put() calls that schedule more RCU callbacks after the\nwait completes, gfs2_put_super() will proceed to free the superblock\nwhile RCU callbacks referencing it are still pending.\nAdd an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure\nall pending RCU callbacks (including gfs2_qd_dealloc) have completed\nbefore the superblock is freed.", "A flaw was found in the Linux kernel's GFS2 file system. This use-after-free vulnerability occurs when the `gfs2_qd_dealloc` function attempts to access memory that has already been released during the unmounting process. This can lead to system instability or crashes, potentially resulting in a denial of service for affected systems."], "name": "CVE-2026-63804", "public_date": "2026-07-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-63804\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-63804\nhttps://lore.kernel.org/linux-cve-announce/2026071902-CVE-2026-63804-8035@gregkh/T"], "threat_severity": "Moderate"}

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