High 7.5Published May 7, 2026

CVE-2026-39820Quadratic string concatentation in consumeComment in net/mail

Updated under an hour ago (Oct 27, 2026, 1:50 PM ET)

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It affects Go standard library net/mail and 59 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Go standard library net/mail

Exploited in the last 30 days

Well-crafted inputs reaching ParseAddress, ParseAddressList, and ParseDate were able to trigger excessive CPU exhaustion and memory allocations.

CVSS: 7.5 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-407, CWE-606
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Go
NVD analysis: Modified
Record last updated: Sep 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Go standard library net/mail go_standard_library:net_mail (from the name)	before 1.25.10; from 1.26.0-0 before 1.26.3	CNA record
Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 8 redhat:ansible_automation_platform	from 0:2.5.10-7.el8ap not affected	CISA ADP
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux	from 0:1.26.3-4.el10_2 not affected	CISA ADP
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support redhat:enterprise_linux_eus	from 0:1.26.5-1.el10_0 not affected	CISA ADP
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service redhat:rhel_tus	from 0:75-10.el8_8 not affected	CISA ADP
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions redhat:rhel_e4s	from 0:75-10.el8_8 not affected	CISA ADP
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support redhat:rhel_eus	from 0:1.26.5-1.el9_6 not affected	CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.12 redhat:openshift	from 0:1.25.5-34.rhaos4.12.git6120b13.el8 not affected	CISA ADP
Red Hat RHEM 1.1 for RHEL 10 redhat:edge_manager	from 0:1.1.4-1.el10em not affected	CISA ADP
Red Hat Cert Manager support for Red Hat OpenShift release 1.19 redhat:cert_manager	from 1786613805 not affected	CISA ADP
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References

References

https://go.dev/issue/78566	issue-tracking
https://go.dev/cl/759940	patch
https://groups.google.com/g/golang-announce/c/qcCIEXso47M	issue-tracking, mailing-list
https://pkg.go.dev/vuln/GO-2026-4986	vendor-advisory
https://access.redhat.com/errata/RHSA-2026:22112
https://access.redhat.com/errata/RHSA-2026:22120
https://access.redhat.com/errata/RHSA-2026:22121
https://access.redhat.com/errata/RHSA-2026:23262
https://access.redhat.com/errata/RHSA-2026:23264
https://access.redhat.com/errata/RHSA-2026:33120
1–10 of 25

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.