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How to verify CVE-2021-26691

Confirm whether your systems are actually affected — run the exact detection check below (Nuclei command or OpenVAS NVT). Detection only; it does not exploit.

How to verify this vulnerability

Scanner data tells you how to confirm whether your systems are actually affected — not just that the CVE exists. Run a Nuclei template against your target for a yes/no answer in seconds.

What's a Nuclei template? Nuclei is a free, open-source scanner. A template is a small YAML rule that probes a target and reports whether it's vulnerable. Runs locally, no agent.
1 · AUTOMATEDDetection command
nuclei -t CVE-2021-26691.yaml -u https://your-target -rl 50 -timeout 10

Community template — download the YAML from GitHub first, then run the command against your own host.

1 Nuclei template
  • criticalAI-generatedhttpApache HTTP Server Heap OverflowGitHub ↗

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This template is on GitHub already — an account lets you search and filter every CVE that has one, not just this CVE.

Nuclei References

Verify with OpenVAS

Greenbone/OpenVAS ships 45 NVT checks for CVE-2021-26691. OpenVAS detects this CVE by NVT OID — enable the NVT in your scan config, or confirm it is in your feed with the query below.

Confirm the NVT is in your feed (GMP)
gvm-cli socket --xml "<get_nvts nvt_oid='1.3.6.1.4.1.25623.1.0.112896' details='1'/>"
NVT OIDs (45)
  • 1.3.6.1.4.1.25623.1.0.112896since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.112897since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.152630since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.704937since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.818440since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.818569since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.844982since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.853882since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.853930since 2026-06-25
  • 1.3.6.1.4.1.25623.1.0.884194since 2026-06-25

+ 35 more NVTs

New to OpenVAS? Greenbone documentation ↗
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