CVE-2026-63993 (GCVE-0-2026-63993)
Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-08-05 12:37
VLAI
EPSS
VEX
Title
vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
Summary
In the Linux kernel, the following vulnerability has been resolved:
vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
skb_tunnel_check_pmtu() can change skb->head.
Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.
Use instead ip_hdr(skb) as done in drivers/net/bareudp.c
and drivers/net/geneve.c.
Found by Sashiko.
Severity
9.8 (Critical)
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 6b8bfce9d2f774d2c2243e0248e03efb99bba6c0
(git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 9257f56ac47ef1976bcd056cf986a9988eeec67a (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 8d435d68d71fb875876b722f4136caf74f2f48bd (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < dc3bfa050f873371e745bdf478b1f5b738e5733d (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 609e63312c29aad18026a1d3222e123d4b6b0feb (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 5303925e360527243b46a440a04667826bbc72b7 (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < a493efd4336cf19122ae0e4cbb3d31b32d70deea (git) Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 7d9ef0cb271555d8cf39fefe6c981e1493b25ecf (git) |
guessed | |
| Linux | Linux |
Affected:
5.9
Unaffected: 0 , < 5.9 (semver) Unaffected: 5.10.259 , ≤ 5.10.* (semver) Unaffected: 5.15.210 , ≤ 5.15.* (semver) Unaffected: 6.1.176 , ≤ 6.1.* (semver) Unaffected: 6.6.143 , ≤ 6.6.* (semver) Unaffected: 6.12.93 , ≤ 6.12.* (semver) Unaffected: 6.18.35 , ≤ 6.18.* (semver) Unaffected: 7.0.12 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
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"product": "Linux",
"programFiles": [
"drivers/net/vxlan/vxlan_core.c"
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"status": "unaffected",
"version": "5.10.259",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "5.15.210",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.176",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.143",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.93",
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},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.35",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "7.0.12",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
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"vulnerable": true
},
{
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}
],
"negate": false,
"operator": "OR"
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\n\nskb_tunnel_check_pmtu() can change skb-\u003ehead.\n\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\n\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\n\nFound by Sashiko."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is in VXLAN transmit processing reached when network-originated packets are decapsulated, bridged, and re-encapsulated; VXLAN is a UDP-based overlay protocol reachable from remote peers over the network.\nAC:L - An attacker can reliably trigger the bug by sending crafted oversized inner IPv4/IPv6 packets (e.g., with DF set or ICMP/ICMPv6 payloads) through a bridged VXLAN interface to force skb_tunnel_check_pmtu() to reallocate skb-\u003ehead yet return 0, leaving the cached ip_hdr pointer stale.\nPR:N - Exploitation requires only the ability to send VXLAN/inner IP traffic to a host with an active VXLAN bridge port; no local account, capabilities, or authentication on the victim is needed.\nUI:N - No victim user action is required beyond normal network operation; triggering the bug is entirely driven by attacker-supplied packets forwarded through the VXLAN device.\nS:U - The vulnerability corrupts kernel heap memory on the host processing the VXLAN traffic; impact remains within the kernel\u0027s security authority and does not inherently cross a VM or sandbox boundary.\nC:H - This is a use-after-free where ip_tunnel_ecn_encap() reads from a freed skb head via the stale cached ip_hdr pointer, enabling kernel memory disclosure and supporting further exploitation.\nI:H - Use-after-free on skb data provides a foundation for heap grooming and arbitrary memory write primitives that could be leveraged for kernel code execution or privilege escalation.\nA:H - The UAF can cause kernel oops/panic during transmit processing and is independently exploitable for denial of service even when full code execution is not achieved."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:37:57.287Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0"
},
{
"url": "https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a"
},
{
"url": "https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd"
},
{
"url": "https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d"
},
{
"url": "https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb"
},
{
"url": "https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"
},
{
"url": "https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea"
},
{
"url": "https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf"
}
],
"title": "vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-63993",
"datePublished": "2026-07-19T14:56:13.218Z",
"dateReserved": "2026-07-19T07:54:57.025Z",
"dateUpdated": "2026-08-05T12:37:57.287Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
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"cve": "CVE-2026-63993",
"date": "2026-10-02",
"epss": "0.00514",
"percentile": "0.41687"
},
"nvd": {
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],
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"versions": [
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{
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},
{
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"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
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"version": "6.1.176",
"versionType": "semver"
},
{
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"version": "6.6.143",
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{
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},
{
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{
"lessThanOrEqual": "7.0.*",
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"version": "7.0.12",
"versionType": "semver"
},
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"version": "7.1",
"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\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\n\nskb_tunnel_check_pmtu() can change skb-\u003ehead.\n\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\n\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\n\nFound by Sashiko."
}
],
"id": "CVE-2026-63993",
"lastModified": "2026-07-30T14:51:11.223",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-07-19T16:17:38.823",
"references": [
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"url": "https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"
},
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},
{
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"url": "https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0"
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},
{
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{
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{
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},
{
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"url": "https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
},
"redhat_vex": {
"aggregate_severity": "Important",
"current_release_date": "2026-09-08T19:41:41+00:00",
"cve": "CVE-2026-63993",
"id": "CVE-2026-63993",
"initial_release_date": "2026-07-19T00:00:00+00:00",
"product_status:fixed": "309",
"product_status:known_affected": "108",
"product_status:known_not_affected": "91",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63993.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-09-30T15:06:29Z",
"cve": "CVE-2026-63993",
"id": "CVE-2026-63993",
"initial_release_date": "2026-07-21T13:01:59Z",
"product_status:known_affected": "279",
"product_status:known_not_affected": "76",
"product_status:recommended": "187",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-63993",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63993.json",
"version": "7"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
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