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CVE-2026-56329VulnerabilityPublished

Capgo before 12.128.2 contains a cross-tenant preview namespace collision vulnerability caused by non-bijective decoding of double underscores to dots in preview hostname parsing

Affects capgoSource GCVE Database

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Not known to be exploited · CVSS 6.4 Medium : upgrade to 12.128.2 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score
6.4Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 12.128.2
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 29 Oct 2026.

What to do

Upgrade cap-go/capgo to 12.128.2.

Affected software

ProductAffectedFixed in
GitHubcap-go/capgopkg:github/cap-go/capgoOther threatsAffected
  • <12.128.2
Fixed in
  • 12.128.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid registering app IDs with underscores that could collide with dotted app IDs or restrict app ID registration policies if possible.

Description

Capgo before 12.128.2 contains a cross-tenant preview namespace collision vulnerability caused by non-bijective decoding of double underscores to dots in preview hostname parsing. Attackers can register app IDs with underscores that collide with other tenants' dotted app IDs, causing preview misrouting and denial of preview access for victim applications.

References

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