🛡️ CVE-2026-27145 — golang
Description
Inefficient candidate hostname parsing in crypto/x509
(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname.
With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.
How this vulnerability can be exploited
This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability high.
CVSS metrics in full
The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
- Attack vector: Network — reachable from anywhere that can route to the service.
- Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
- Privileges required: None — an unauthenticated stranger can try it.
- User interaction: None — nobody has to be tricked into anything.
- Scope: Unchanged — the damage stays inside the vulnerable component.
- Confidentiality impact: None.
- Integrity impact: Low — limited, and the attacker does not choose what is affected.
- Availability impact: High — total loss, or loss the attacker controls.
Affected software
CVE-2026-27145 is recorded against 3 packages.
- golang
- stdlib
- unknown
Timeline and source
Published on 5 June 2026 and last revised on 17 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.
References
go.dev (Web)
go.dev (Web)
groups.google.com (Web)
nvd.nist.gov (Web)
pkg.go.dev (Web)
access.redhat.com (Web)
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bugzilla.redhat.com (Web)
security.access.redhat.com (Web)
access.redhat.com (Web)
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access.redhat.com (Web)
access.redhat.com (Web)
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access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
access.redhat.com (Web)
Other advisories for this package
golang has other advisories on record. If you are patching this one, these are worth checking on the same host:
- CVE-2026-46600 (8.0 High, published 17 Aug 2026)
- RHSA-2026:7876 (published 5 Aug 2026)
- RHSA-2025:21816 (published 5 Aug 2026)
- RHSA-2026:47719 (published 30 Jul 2026)
- RHSA-2026:47712 (published 30 Jul 2026)
- RHSA-2026:0921 (published 25 Jul 2026)
- RHSA-2025:22668 (published 24 Jul 2026)
- RHSA-2025:23737 (published 24 Jul 2026)
CVE-2026-27145 on other distributions
Each distribution ships its own build and its own fixed version. Pick the one you run:
Details
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| golang | — | — |
| stdlib | — | — |
| unknown | — | — |
References
Similar Threats
- Unknown ALSA-2024:2562
- Unknown ALSA-2024:1963
- Unknown ALSA-2024:1962
- Unknown ALSA-2024:1462
- Unknown ALSA-2024:1472
Vulnerability Monitoring
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