Authentication bypass via timing-dependent digest validation
Published May 4, 2026 · Updated May 4, 2026
Observable timing discrepancy in mod_auth_digest in Apache HTTP Server 2.4.66 and earlier allows remote attackers to bypass Digest authentication. The request parser accepts nonces and response digests without enforcing their fixed lengths, exposing timing differences during validation. The server must load mod_auth_digest and protect a reachable location with AuthType Digest; successful bypass grants authenticated access.
Summary
What happened
Observable timing discrepancy in mod_auth_digest in Apache HTTP Server 2.4.66 and earlier allows remote attackers to bypass Digest authentication. The request parser accepts nonces and response digests without enforcing their fixed lengths, exposing timing differences during validation. The server must load mod_auth_digest and protect a reachable location with AuthType Digest; successful bypass grants authenticated access.
The record
- CVE
- CVE-2026-33006
- Published
- May 4, 2026
- Updated
- May 4, 2026
- Vendor
- The Apache Software Foundation
- Product
- Apache HTTP Server
- Classifications
- CWE-208, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 4, 2026CVE publishedPublication date reported by the CVE source.
- May 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=2.4.66
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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