Filter bypass via overflowing port number
Published Nov 26, 2025 · Updated Nov 26, 2025
Integer overflow in Tinyproxy 1.11.2 and earlier allows remote attackers to bypass URL filter rules with an oversized port number. strip_return_port() parses the decimal port into a signed integer without range validation, so adding 2^32 wraps a blocked port to its original value. The proxy must use host-and-port URL filtering; a crafted absolute URL then reaches a backend service whose ordinary port is denied.
Summary
What happened
Integer overflow in Tinyproxy 1.11.2 and earlier allows remote attackers to bypass URL filter rules with an oversized port number. strip_return_port() parses the decimal port into a signed integer without range validation, so adding 2^32 wraps a blocked port to its original value. The proxy must use host-and-port URL filtering; a crafted absolute URL then reaches a backend service whose ordinary port is denied.
The record
- CVE
- CVE-2025-63938
- Published
- Nov 26, 2025
- Updated
- Nov 26, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-190, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 26, 2025CVE publishedPublication date reported by the CVE source.
- Nov 26, 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.
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
- Tinyproxy oversized-port filter-bypass proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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