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CVE Record

CVE-2023-53600: tunnels: fix kasan splat when generating ipv4 pmtu error

In the Linux kernel, the following vulnerability has been resolved: tunnels: fix kasan splat when generating ipv4 pmtu error If we try to emit an icmp error in response to a nonliner skb, we get BUG: KASAN: slab-out-of-bounds in ip_compute_csum+0x134/0x220 Read of size 4 at addr ffff88811c50db00 by task iperf3/1691 CPU: 2 PID: 1691 Comm: iperf3 Not tainted 6.5.0-rc3+ #309 [..] kasan_report+0x105/0x140 ip_compute_csum+0x134/0x220 iptunnel_pmtud_build_icmp+0x554/0x1020 skb_tunnel_check_pmtu+0x513/0xb80 vxlan_xmit_one+0x139e/0x2ef0 vxlan_xmit+0x1867/0x2760 dev_hard_start_xmit+0x1ee/0x4f0 br_dev_queue_push_xmit+0x4d1/0x660 [..] ip_compute_csum() cannot deal with nonlinear skbs, so avoid it. After this change, splat is gone and iperf3 is no longer stuck.

CriticalCVSS 9.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A Linux tunnel-networking flaw can read beyond a packet buffer when generating certain IPv4 path-MTU error messages. The reported outcome was a kernel memory-safety warning and a stuck iperf3 workload. The supplied evidence does not demonstrate data theft, code execution, or real-world exploitation.

Executive priority

Prioritize prompt remediation on production tunnel gateways, virtualized networking hosts, and other VXLAN users. Although the supplied rating is critical, demonstrated impact is currently limited to an out-of-bounds read and workload stall, with no evidence of active exploitation.

Technical view

When an IPv4 PMTU ICMP error is built for a nonlinear socket buffer, ip_compute_csum receives an unsupported buffer layout, causing a KASAN slab-out-of-bounds read in the VXLAN transmission path. The kernel fix avoids that checksum operation.

Likely exposure

The bundle lists Linux 5.9, 5.10.191, 5.15.127, 6.1.46, 6.4.11, and 6.5 as affected; its separate “0” entry is ambiguous. Exposure is most relevant to systems using tunnel networking, including VXLAN, where the affected PMTU error path can execute.

Exploitation context

The CVSS vector describes network reachability without privileges or user interaction, but the supplied technical description does not establish practical remote exploitation requirements. The CVE is not listed as KEV, and no cited source reports active exploitation. Treat exploitation status as unconfirmed.

Researcher notes

Version metadata is incomplete and includes an ambiguous “0” entry, so upstream numbers should not be treated as definitive distribution-package boundaries. The source demonstrates the faulty call path and observed denial-of-service-like behavior, but does not document exploitability, disclosure of kernel memory, or code execution.

Mitigation direction

  • Upgrade to a vendor-supported kernel containing the cited stable fix.
  • Consult the operating-system vendor for exact fixed package versions.
  • Prioritize exposed tunnel endpoints and infrastructure using VXLAN.
  • If immediate upgrading is impossible, review vendor guidance for supported temporary mitigations.

Validation and detection

  • Inventory running kernel versions on tunnel and VXLAN hosts.
  • Map distribution packages to the cited upstream stable fixes.
  • Confirm upgraded systems booted into the corrected kernel.
  • Monitor kernel logs for KASAN, checksum, tunnel, or PMTU-related faults.
  • Retest representative tunneled traffic and IPv4 PMTU handling after remediation.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2023-53600 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
6Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H3.95.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

9.1Critical
CVSS 3.1 vector shape for CVE-2023-53600Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux4cb47a8644cc9eb8ec81190a50e79e6530d0297f, 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, 4cb47a8644cc9eb8ec81190a50e79e6530d0297funaffected
LinuxLinux5.9, 0, 5.10.191, 5.15.127, 6.1.46, 6.4.11, 6.5affected
Weakness

CWE details

No CWE listed

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