CVE-2021-21777Public exploitNetwork attack vector

Memory disclosure via signed UDP length conversion

Published Jun 17, 2021 · Updated Aug 3, 2024

Out-of-bounds read in EIP Stack Group OpENer 2.3 and commit 8c73bf3 allows remote attackers to disclose process memory via UDP. CheckAndHandleUdpUnicastSocket passes packet data into a parser whose signed length calculation can move the receive cursor before the packet buffer. Unauthenticated UDP access is sufficient; matching memory bytes are returned, while alternate crafted lengths can hang the service or generate reflected traffic.

CVSS severity10.0
Critical
EPSS probability1.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in EIP Stack Group OpENer 2.3 and commit 8c73bf3 allows remote attackers to disclose process memory via UDP. CheckAndHandleUdpUnicastSocket passes packet data into a parser whose signed length calculation can move the receive cursor before the packet buffer. Unauthenticated UDP access is sufficient; matching memory bytes are returned, while alternate crafted lengths can hang the service or generate reflected traffic.

The record

CVE
CVE-2021-21777
Published
Jun 17, 2021
Updated
Aug 3, 2024
Vendor
EIP Stack Group
Product
OpENer
Classifications
CWE-125, T1498.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 17, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=EIP Stack Group OpENer 2.3 ,EIP Stack Group OpENer development commit 8c73bf3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

EIP Stack Group · OpENerversion=EIP Stack Group OpENer 2.3 ,EIP Stack Group OpENer development commit 8c73bf3

Published CVSS scores

10.0NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:H
8.6Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
9.4NIST NVDAV:N/AC:L/Au:N/C:C/I:N/A:C

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 exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1498.002Network Denial of Service Reflection Amplification

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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