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GO-2026-4977 BIT-golang-2026-42499 CVE-2026-42499

Quadratic string concatenation in consumePhrase in net/mail

High Go
Severity
7.5 / 10
High · CVSS 3.1
Exploit chance (EPSS)
0.80%
Chance of exploitation in the next 30 days. Higher than 56.52% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-1046 Creation of Immutable Text Using String Concatenation
Fix
1.26.3
Upgrade stdlib to this version or later

Description

Pathological inputs could cause DoS through consumePhrase when parsing an email address according to RFC 5322.

Affected versions

Go

PackageVulnerableFixed in
stdlib
< 1.25.10
>= 1.26.0-0, < 1.26.3
1.25.10
1.26.3

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

stdlib Go → 1.26.3

go
go get stdlib@v1.26.3 && go mod tidy

Severity breakdown

CVSS 3.1 7.5

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

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Weakness

CWE-1046: Creation of Immutable Text Using String Concatenation

The product creates an immutable text string using string concatenation operations.

References

Advisories

Fixes and patches

Issue reports

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
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RUSTSEC-2026-0382
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GO-2026-6613
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GO-2026-6609
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GO-2026-6608
Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart
High Also affects stdlib
GO-2026-6607
Reject malformed ECH outer extension references in crypto/tls
High Also affects stdlib
GO-2026-6604
Root.Mkdir(All) can follow junctions out of the root on Windows in os
Critical Also affects stdlib
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