CVE-2020-24837Network attack vector

Payment processing interruption via unsigned period underflow

Published Feb 10, 2021 · Updated Aug 4, 2024

Integer underflow in ZCFees allows remote attackers to block process() execution by influencing the transaction timestamp. The process() function subtracts unsigned lastPeriodExecIdx from currPeriodIdx without first ensuring that the current period is not earlier, causing wraparound when the timestamp-derived index regresses. Exploitation requires influence over the transaction timestamp, and the documented consequence is interruption of fee-payment processing.

CVSS severity7.5
High
EPSS probability1.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in ZCFees allows remote attackers to block process() execution by influencing the transaction timestamp. The process() function subtracts unsigned lastPeriodExecIdx from currPeriodIdx without first ensuring that the current period is not earlier, causing wraparound when the timestamp-derived index regresses. Exploitation requires influence over the transaction timestamp, and the documented consequence is interruption of fee-payment processing.

The record

CVE
CVE-2020-24837
Published
Feb 10, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-191
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 10, 2021CVE 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:H/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/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-191Integer Underflow (Wrap or Wraparound)

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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