CVE-2021-27877Known exploitationPublic exploitNetwork attack vector

Unauthenticated privileged command execution via legacy SHA authentication

Published Mar 1, 2021 · Updated Oct 21, 2025

Improper authentication in Veritas Backup Exec Agent before 21.2 allows remote attackers to execute privileged commands. The agent leaves its obsolete SHA authentication scheme enabled, allowing crafted remote authentication to establish an unauthorized session. No credentials or user interaction are required, and commands run with the agent's elevated operating-system privileges.

CVSS severity8.2
High
EPSS probability64.91%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Veritas Backup Exec Agent before 21.2 allows remote attackers to execute privileged commands. The agent leaves its obsolete SHA authentication scheme enabled, allowing crafted remote authentication to establish an unauthorized session. No credentials or user interaction are required, and commands run with the agent's elevated operating-system privileges.

The record

CVE
CVE-2021-27877
Published
Mar 1, 2021
Updated
Oct 21, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 22, 2022Exploitation reportedUNC4466 ALPHV ransomware intrusion
  3. Oct 21, 2025Record 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

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2VeritasCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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 exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

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

Reported exploitation

Technologies

Your stack

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Your stack

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