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CVE-2021-27877

9.8, critical Known exploited Used in ransomware

Veritas Backup Exec Agent Improper Authentication Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
9.8, critical critical CVSS v3.1
EPSS, next 30 days
65% higher than 99.2% of scored CVEs
Exploitation
Confirmed in the wild
Published
1 Mar 20215 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 7 Apr 2023 and links it to ransomware activity. US federal agencies had to remediate by 28 Apr 2023, a deadline that has passed.

Required action. Apply updates per vendor instructions.

Description

An issue was discovered in Veritas Backup Exec before 21.2. It supports multiple authentication schemes: SHA authentication is one of these. This authentication scheme is no longer used in current versions of the product, but hadn't yet been disabled. An attacker could remotely exploit this scheme to gain unauthorized access to an Agent and execute privileged commands.

Details

Vendor
Veritas
Product
Backup Exec
Weakness
n/a
Status
Analyzed
Updated
17 Jun 2026
Assigner
cve@mitre.org

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References 3

Exploit code 1

Advisories 1

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Veritas CVEs

Every Veritas CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2021-27876 Veritas Backup Exec Agent File Access Vulnerability KEV EPSS 14% 8.1, high
  • CVE-2021-27878 Veritas Backup Exec Agent Command Execution Vulnerability KEV EPSS 24% 8.8, high

Beyond this page

Is CVE-2021-27877 in your network?

This page tells you how dangerous CVE-2021-27877 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2021-27877 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2021-27877 comes with the devices to patch.

    Learn more about EXYS7600 OCELOT

  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.