Proxy bypass via IPv6 zone-ID hostname matching
Published Mar 12, 2025 · Updated Apr 16, 2026
Proxy bypass in Go net/http 1.23.6 and earlier or 1.24.0, and x/net before 0.36.0, allows attackers to avoid a configured proxy. The NO_PROXY matcher compares an IPv6 zone identifier with domain suffix patterns as if the zone text were part of the hostname, causing a crafted literal to match an unrelated exclusion and route directly. Exploitation requires a consuming application that accepts attacker-influenced IPv6 destinations and relies on matching NO_PROXY patterns; the demonstrated consequence is proxy-policy bypass, not code execution.
Summary
What happened
Proxy bypass in Go net/http 1.23.6 and earlier or 1.24.0, and x/net before 0.36.0, allows attackers to avoid a configured proxy. The NO_PROXY matcher compares an IPv6 zone identifier with domain suffix patterns as if the zone text were part of the hostname, causing a crafted literal to match an unrelated exclusion and route directly. Exploitation requires a consuming application that accepts attacker-influenced IPv6 destinations and relies on matching NO_PROXY patterns; the demonstrated consequence is proxy-policy bypass, not code execution.
The record
- CVE
- CVE-2025-22870
- Published
- Mar 12, 2025
- Updated
- Apr 16, 2026
- Vendor
- Go
- Product
- golang.org/x/net/proxy
- Classifications
- CWE-115, CWE-20
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 12, 2025CVE publishedPublication date reported by the CVE source.
- Apr 16, 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 <0.36.0
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.
Public exploit references
- CVE-2025-22870 HTTP proxy-bypass proof of conceptproof of concept · demonstrated
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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