Memory corruption via unbounded year formatting
Published Jun 6, 2021 · Updated Dec 5, 2025
Buffer overflow in the autoindex module in NGINX before 1.13.6 allows remote attackers to corrupt worker memory via a directory request. ngx_gmtime converts a negative time_t to an unsigned value and writes a year longer than the four digits reserved by date-format buffers. Autoindex must be enabled and encounter a file whose modification time produces a year beyond four digits; the public report demonstrates malformed date output but does not establish code execution or a reliable crash.
Summary
What happened
Buffer overflow in the autoindex module in NGINX before 1.13.6 allows remote attackers to corrupt worker memory via a directory request. ngx_gmtime converts a negative time_t to an unsigned value and writes a year longer than the four digits reserved by date-format buffers. Autoindex must be enabled and encounter a file whose modification time produces a year beyond four digits; the public report demonstrates malformed date output but does not establish code execution or a reliable crash.
The record
- CVE
- CVE-2017-20005
- Published
- Jun 6, 2021
- Updated
- Dec 5, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 6, 2021CVE publishedPublication date reported by the CVE source.
- Dec 5, 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?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
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
- ngx_gmtime date-overflow reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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