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CVE-2021-25737 (GCVE-0-2021-25737)

Vulnerability from cvelistv5 – Published: 2021-09-06 11:32 – Updated: 2024-09-16 21:04
VLAI
Title
Holes in EndpointSlice Validation Enable Host Network Hijack
Summary
A security issue was discovered in Kubernetes where a user may be able to redirect pod traffic to private networks on a Node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.
CWE
Impacted products
Vendor Product Version CPE status
Kubernetes Kubernetes Affected: unspecified , ≤ 1.18.18 (custom)
Affected: unspecified , ≤ 1.19.10 (custom)
Affected: unspecified , ≤ 1.20.6 (custom)
Affected: unspecified , ≤ 1.21.0 (custom)
guessed Create a notification for this product.
Date Public
2021-05-18 00:00
Show details on NVD website

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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

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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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