CVE-2021-41615Network attack vector

HTTP Digest challenge prediction via hardcoded nonce secret

Published Aug 8, 2022 · Updated Aug 4, 2024

Insufficient nonce entropy in EmbedThis GoAhead WebServer 2.1.8 allows remote attackers to predict HTTP Digest authentication nonces. The websda.c nonce calculation derives its challenge from the hardcoded onceuponatimeinparadise value rather than secret server data. The flaw is reachable when HTTP Digest protects a resource; predictable challenges weaken authentication freshness, but the published record does not demonstrate access without a valid password.

CVSS severity9.8
Critical
EPSS probability1.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient nonce entropy in EmbedThis GoAhead WebServer 2.1.8 allows remote attackers to predict HTTP Digest authentication nonces. The websda.c nonce calculation derives its challenge from the hardcoded onceuponatimeinparadise value rather than secret server data. The flaw is reachable when HTTP Digest protects a resource; predictable challenges weaken authentication freshness, but the published record does not demonstrate access without a valid password.

The record

CVE
CVE-2021-41615
Published
Aug 8, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-331, CAPEC-59
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 8, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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

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 exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-331Insufficient Entropy
CAPEC-59Session Credential Falsification through Prediction

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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