Worker memory disclosure via failed authentication parsing
Published Aug 13, 2025 · Updated Nov 4, 2025
Out-of-bounds read in F5 NGINX Open Source and NGINX Plus allows remote attackers to disclose worker memory during SMTP authentication. Failed Base64 decoding can leave session login or password fields inconsistent, and later auth_http request construction reads beyond the intended buffer. Exploitation requires the SMTP module, smtp_auth none, and an Auth-Wait response; disclosed bytes are sent only to the authentication server.
Summary
What happened
Out-of-bounds read in F5 NGINX Open Source and NGINX Plus allows remote attackers to disclose worker memory during SMTP authentication. Failed Base64 decoding can leave session login or password fields inconsistent, and later auth_http request construction reads beyond the intended buffer. Exploitation requires the SMTP module, smtp_auth none, and an Auth-Wait response; disclosed bytes are sent only to the authentication server.
The record
- CVE
- CVE-2025-53859
- Published
- Aug 13, 2025
- Updated
- Nov 4, 2025
- Vendor
- F5 Networks
- Product
- NGINX Open Source
- Classifications
- CWE-125, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 13, 2025CVE publishedPublication date reported by the CVE source.
- Nov 4, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0.7 <1.29.1
What conditions does exploitation require?
What is affected?
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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