CVE-2021-33403Public exploitNetwork attack vector

Financial loss via unchecked recipient-balance addition

Published Aug 3, 2021 · Updated Aug 3, 2024

Integer overflow in Lancer Token allows remote authenticated users to reduce account balances through a crafted token transfer. The transfer function adds the supplied value to balances[_to] without checking whether the uint256 sum exceeds 2^256, so the recipient balance wraps to a smaller number. Exploitation requires contract-owner access and two sufficiently large balances; the resulting balance corruption causes direct financial loss.

CVSS severity7.5
High
EPSS probability1.20%
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 Lancer Token allows remote authenticated users to reduce account balances through a crafted token transfer. The transfer function adds the supplied value to balances[_to] without checking whether the uint256 sum exceeds 2^256, so the recipient balance wraps to a smaller number. Exploitation requires contract-owner access and two sufficiently large balances; the resulting balance corruption causes direct financial loss.

The record

CVE
CVE-2021-33403
Published
Aug 3, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190, T1657
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Aug 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 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 privilegesadmin

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1657Financial Theft

Public exploit references

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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