CVE-2020-21699Network attack vector

Cache metadata disclosure via overflowing range totals

Published Aug 22, 2023 · Updated Oct 3, 2024

Integer overflow in Tengine 2.2.2's Nginx range filter allows remote attackers to disclose cache metadata via crafted HTTP Range requests. The ngx_http_range_parse function adds each parsed byte-range length to a cumulative size without checking whether the addition exceeds the offset type, allowing the total to wrap and accept negative-start ranges. Exploitation requires an unauthenticated request for a cached response; standard modules expose the cache-file header, and no broader standard-module impact is reported.

CVSS severity7.5
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Tengine 2.2.2's Nginx range filter allows remote attackers to disclose cache metadata via crafted HTTP Range requests. The ngx_http_range_parse function adds each parsed byte-range length to a cumulative size without checking whether the addition exceeds the offset type, allowing the total to wrap and accept negative-start ranges. Exploitation requires an unauthenticated request for a cached response; standard modules expose the cache-file header, and no broader standard-module impact is reported.

The record

CVE
CVE-2020-21699
Published
Aug 22, 2023
Updated
Oct 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 3, 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:H/I:N/A:N

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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