CVE-2020-8659Network attack vector

Denial of service via HTTP chunk fragmentation

Published Mar 4, 2020 · Updated Aug 4, 2024

Denial of service in CNCF Envoy 1.13.0 and earlier allows remote attackers to exhaust memory with many small HTTP/1.1 chunks. The HTTP/1 codec allocates a separate buffer fragment rounded to 4 KiB for each chunk and retains empty chunks after committing data. No authentication or user interaction is required; memory use can exceed configured buffer limits by two to three orders of magnitude and interrupt proxy service.

CVSS severity7.5
High
EPSS probability1.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in CNCF Envoy 1.13.0 and earlier allows remote attackers to exhaust memory with many small HTTP/1.1 chunks. The HTTP/1 codec allocates a separate buffer fragment rounded to 4 KiB for each chunk and retains empty chunks after committing data. No authentication or user interaction is required; memory use can exceed configured buffer limits by two to three orders of magnitude and interrupt proxy service.

The record

CVE
CVE-2020-8659
Published
Mar 4, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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