VulnerabilityPublished 13 Nov 2026

CVE-2026-126348: Mikutter · Addressable display_uri can show misleading hosts with invalid Punycode A-labels

Affects mikutterSource GCVE Database

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Authoritative record:CVE-2026-126348· Medium 4.3

Not known to be exploited · CVSS 4.3 Medium · fixed in 2.9.1 : update mikutter when convenient.

Data as of 13 Nov 2026, 21:02 UTC

CVSS 3.1 base score

4.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	4.3

Patch: Available – fixed in 2.9.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewmikutter`pkg:brew/mikutter`Other threats	Affected >=3.4.6	Fixed in–

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Description

### Impact `Addressable::IDNA.to_unicode`, in the pure-Ruby IDNA implementation, decodes Punycode labels (labels beginning with `xn--`) that are not valid A-labels. Those labels are returned in decoded form, when they should be returned unchanged. That includes: - labels that decode to only ASCII characters, e.g. `xn--google-` decodes to `google`; - labels that decode to text that doesn't convert back to the same label (RFC 3490 §4.2), e.g. text that isn't in normalized form. `Addressable::URI#display_uri` uses `to_unicode`, so for `https://xn--google-.example.org/` it displays the host `google.example.org`, while `#host`, `#normalized_host` and any connection made from the URI use `xn--google-.example.org`. An attacker who controls a domain can therefore have a URI displayed as a host they don't control. Applications that compare the result of `to_unicode` against a list of trusted names can likewise treat two different hosts as the same. The native IDNA implementation, used when libidn and the `idn-ruby` gem are installed, is not affected. `to_ascii` and `normalized_host` are not affected. ### Affected Versions This vulnerability affects Addressable >= 2.0.0, the first version with the pure-Ruby IDNA implementation, when that implementation is in use. It is fixed in 2.9.1, where such labels are returned unchanged, as with libidn. ### Workarounds - Install libidn and the `idn-ruby` gem, so that Addressable uses the native IDNA implementation. - Don't make security decisions on `display_uri` or `to_unicode` output. Compare hosts using `normalized_host`. ### Credits Reported by @tonghuaroot. ### For more information If there are any questions or comments about this advisory: * [Open an issue](https://github.com/sporkmonger/addressable/issues)

References

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