CVE-2021-25835Public exploitNetwork attack vector

Unauthorized cross-chain transfers via replayed signatures

Published Feb 8, 2021 · Updated Aug 3, 2024

Cross-chain transaction replay in Cosmos Network Ethermint 0.4.0 and earlier allows remote attackers to execute signed transfers on another chain. EVM transaction validation treats distinct chain IDs with the same numeric chainIDEpoch as equivalent and accepts the same signed message under Ethermint's Ethereum-compatible signature scheme. Exploitation requires the victim to reuse a key across both chains and the destination account nonce to accept the captured transaction, enabling an unauthorized transfer without altering the signature.

CVSS severity7.5
High
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-chain transaction replay in Cosmos Network Ethermint 0.4.0 and earlier allows remote attackers to execute signed transfers on another chain. EVM transaction validation treats distinct chain IDs with the same numeric chainIDEpoch as equivalent and accepts the same signed message under Ethermint's Ethereum-compatible signature scheme. Exploitation requires the victim to reuse a key across both chains and the destination account nonce to accept the captured transaction, enabling an unauthorized transfer without altering the signature.

The record

CVE
CVE-2021-25835
Published
Feb 8, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-294
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 8, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitPublished

Weakness, pattern, technique

CWE-294Authentication Bypass by Capture-replay

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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