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CVE-2026-39821 is an input-validation vulnerability in the Go golang.org/x/net/idna package. The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to ASCII-only labels instead of rejecting them. Applications that authorize an encoded ASCII hostname before converting it to Unicode can therefore treat two representations of the same hostname differently, allowing an attacker to bypass hostname-based access restrictions and potentially escalate privileges.
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No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
181 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A validation bypass and privilege escalation vulnerability in Punycode label handling, addressed by the SUSE update to golang-github-prometheus-prometheus version 3.13.2.
A privilege-escalation vulnerability caused by incorrect Punycode label processing in golang.org/x/net/idna, referenced in an OpenShift Container Platform security update for RHCOS 4. The listing assigns a CVSS v3 base score of 8.2, with high confidentiality and integrity impacts. Nessus detects affected installations through self-reported version information rather than testing exploitation. Red Hat advisory RHSA-2026:79150 provides the security update.
A vulnerability addressed by the SUSE Multi-Linux Manager 5.1.4 security update. The content does not identify its specific component, vulnerability mechanism, or impact.
A privilege escalation vulnerability involving incorrect Punycode label processing in golang.org/x/net/idna affects a package installed on Red Hat Enterprise Linux CoreOS 4 hosts. The advisory provides remediation through OpenShift Container Platform 4.16.73 package updates under RHSA-2026:77611. The listed CVSS v3 base score is 8.2 (High). Nessus identifies exposure using self-reported version information rather than testing exploitation.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.