CVE-2021-27877

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.

CVSS: 8.2Highscored by the publisher (CNA)
Exploited in the wild: Yes, in CISA KEV since 7 Apr 2023CISA deadline for US federal agencies: 28 Apr 2023known use in ransomware campaignspublic exploit code
EPSS: 64.9%chance of exploitation in the next 30 daystop 0.8% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 1 Mar 2021analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Exploitable: At runtime
Attack vector: network
Can a WAF block it?: Partly. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Products named in our analysis

veritas:backup_exec

Fix and mitigation

WAF and other mitigations

Can a WAF block it? Partly. The bug can be reached over the network, so generic WAF rules may stop some attacks. Its weakness type is unknown, so we cannot be more precise.

Also consider: patch

Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 7 Apr 2023. Known use in ransomware campaigns.
CISA due date: 28 Apr 2023, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: Yes: 1 Metasploit module · 1 GitHub proof of concept · 1 Nuclei template
CISA SSVC: exploitation active, automatable yes, technical impact partialAssessed by CISA 22 Dec 2023 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.

Timeline

1 Mar 2021Published
7 Apr 2023Added to CISA KEV (exploited in the wild)766 days (about 2 years) later
28 Apr 2023CISA remediation due date (US federal agencies)21 days later
22 Dec 2023CISA SSVC assessment: exploitation active238 days (about 8 months) later
21 Oct 2025CVE record last updated670 days (about 2 years) later
2 Jul 2026First public exploit or proof of concept253 days (about 8 months) later
12 Nov 2026Analysed by vulneraibility.com134 days (about 4 months) later

CVSS vector

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

Metric	Value	What it means
Attack vector	NetworkReachable over the internet or any routable network.	Reachable over the internet or any routable network.
Attack complexity	LowRepeatable attack, no special conditions.	Repeatable attack, no special conditions.
Privileges required	NoneThe attacker needs no prior access.	The attacker needs no prior access.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	LowLimited modification possible.	Limited modification possible.
Availability	NoneThe service stays up.	The service stays up.

Common questions

Is CVE-2021-27877 being exploited?

Yes. CVE-2021-27877 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2021-27877?

CVE-2021-27877 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2021-27877?

Yes. A fix has been recorded for CVE-2021-27877. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2021-27877 affect?

CVE-2021-27877 affects veritas:backup_exec. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

3 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile
Metasploit Framework: exploit and scanner modules
Nuclei templates: detection templates
PoC-in-GitHub: GitHub repositories that claim a proof of concept

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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