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CVE Record

CVE-2021-47152: mptcp: fix data stream corruption

In the Linux kernel, the following vulnerability has been resolved: mptcp: fix data stream corruption Maxim reported several issues when forcing a TCP transparent proxy to use the MPTCP protocol for the inbound connections. He also provided a clean reproducer. The problem boils down to 'mptcp_frag_can_collapse_to()' assuming that only MPTCP will use the given page_frag. If others - e.g. the plain TCP protocol - allocate page fragments, we can end-up re-using already allocated memory for mptcp_data_frag. Fix the issue ensuring that the to-be-expanded data fragment is located at the current page frag end. v1 -> v2: - added missing fixes tag (Mat)

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47152 is a Linux kernel MPTCP bug that can corrupt data streams when MPTCP shares page-fragment allocation assumptions with plain TCP paths. The public record describes a transparent proxy reproducer, but does not provide CVSS, CWE, or confirmed real-world abuse.

Executive priority

Treat as a targeted kernel maintenance issue unless MPTCP is operationally important in your environment. Prioritize patch validation for Linux proxies, network appliances, or custom kernels using MPTCP, but current sources do not justify emergency response claims.

Technical view

The flaw is in MPTCP fragment handling, specifically mptcp_frag_can_collapse_to(). It could reuse already allocated memory for mptcp_data_frag when non-MPTCP code also allocates page fragments. Kernel stable commits fix this by ensuring expansion only occurs at the current page-fragment end.

Likely exposure

Exposure is most plausible on Linux systems using MPTCP, especially proxying paths where inbound TCP connections are forced to MPTCP. Exact exposure depends on the distribution kernel, MPTCP configuration, and whether the referenced stable fixes or vendor backports are present.

Exploitation context

The source bundle reports a clean reproducer from the original reporter, but no KEV listing and no cited evidence of active exploitation. The available evidence supports a data-corruption vulnerability, not a confirmed remote compromise scenario.

Researcher notes

Evidence is limited to the CVE description and Linux stable commit references. The affected-version data in the bundle is sparse and partly commit-oriented, so researchers should validate against actual kernel source, distribution backports, and MPTCP runtime configuration.

Mitigation direction

  • Check Linux distribution advisories for CVE-2021-47152 coverage.
  • Update to a vendor kernel containing the referenced stable fixes.
  • Confirm any custom kernel includes the MPTCP fragment fix commits.
  • Reduce unnecessary MPTCP exposure where operationally feasible until patched.

Validation and detection

  • Inventory Linux kernel versions and vendor patch levels.
  • Identify systems with MPTCP enabled or proxy paths using MPTCP.
  • Map installed kernels to vendor advisories or referenced stable commits.
  • Regression-test affected proxy and MPTCP traffic for data integrity after patching.
Prepared
Confidence
medium
Sources
5

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-2021-47152 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux18b683bff89d46ace55f12d00c0440d44d6160c4, 18b683bff89d46ace55f12d00c0440d44d6160c4, 18b683bff89d46ace55f12d00c0440d44d6160c4unaffected
LinuxLinux5.7, 0, 5.10.42, 5.12.9, 5.13affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.