Authentication bypass in Veritas Backup Exec Agent via legacy SHA authentication
CVE-2021-27877 affects Veritas Backup Exec before version 21.2. The product supported multiple authentication schemes, including a legacy SHA-based authentication mechanism. Although this scheme was no longer used in current product operation, it had not been disabled. A remote attacker could exploit the still-enabled legacy authentication path to gain unauthorized access to a Backup Exec Agent and then execute privileged commands on that agent.
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Impact, mitigation & remediation
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Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
Repository is a small standalone Python proof-of-concept/operational exploit consisting of one main script (be_rce.py), a README, and a license. The script targets Veritas Backup Exec Agent over the network on TCP/10000 using NDMP and implements a full exploit chain for CVE-2021-27876, CVE-2021-27877, and CVE-2021-27878. The exploit is not merely a detector: it performs active exploitation. Its core capabilities are: connecting to the NDMP service, performing the custom TLS-related handshake by generating a local CA and signing the agent CSR, abusing the SHA authentication weakness to authenticate as Administrator without a password, invoking NDMP_EXECUTE_COMMAND to run arbitrary OS commands as NT AUTHORITY\SYSTEM, reading command output back from a temporary file via NDMP file operations, and deleting the temporary file afterward. Code structure in be_rce.py includes: XDR serialization/deserialization helpers for NDMP message formatting; an NDMPSock class for framed NDMP send/receive and TLS socket wrapping; certificate helper routines to generate a CA and sign the server CSR; and an exploit entry point that chains connection, handshake, auth bypass, command execution, file open/read/close, and cleanup. The script accepts target and command from the command line, with a hardcoded default target IP if omitted. Notable observables include the NDMP service port 10000, the Windows temp output file C:\Windows\Temp\_be_out.txt, and use of C:\Windows\System32\cmd.exe for execution. The README documents affected versions, usage examples, and remediation guidance. Overall, this is a real standalone network RCE exploit with a basic but functional hardcoded payload flow, making it best classified as OPERATIONAL rather than a framework-integrated or detection-only artifact.
Affected products & vendors
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Recent activity
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.