LiveActive security incident?Get immediate response
CVE Record

CVE-2026-42499: Quadratic string concatenation in consumePhrase in net/mail

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

HighCVSS 7.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-42499 is a denial-of-service issue in Go's net/mail package. Specially crafted email-address input can make parsing consume excessive CPU, potentially slowing or stopping services that parse untrusted email addresses. The supplied sources do not show active exploitation.

Executive priority

Prioritize remediation for internet-facing or mail-processing Go services. The business risk is service disruption, not confidentiality loss, but unauthenticated network reachability makes exposed parsers important to patch promptly.

Technical view

The issue is described as quadratic string concatenation in consumePhrase during RFC 5322 email address parsing. It affects availability only, with CVSS 3.1 score 7.5: network reachable, low complexity, no privileges or user interaction, and high availability impact.

Likely exposure

Exposure is most likely in Go applications that use net/mail to parse email addresses, mailbox lists, or headers from untrusted sources such as forms, APIs, inbound mail, or identity workflows.

Exploitation context

The source bundle marks KEV as false and provides no cited evidence of exploitation in the wild. The attack condition is pathological input reaching net/mail parsing, not code execution or data theft.

Researcher notes

Evidence supports a parser algorithmic-complexity DoS in Go standard library net/mail. The bundle identifies consumePhrase and a Go change list, but does not include exploit details or exact fixed upstream version text, so version validation should follow Go and vendor advisories.

Mitigation direction

  • Upgrade Go to a release containing the Go advisory fix.
  • Apply relevant Red Hat errata where Go packages come from Red Hat.
  • Limit accepted email-address input size before parsing.
  • Avoid parsing untrusted bulk headers without resource controls.
  • Check vendor guidance for exact fixed package versions.

Validation and detection

  • Inventory Go services that import or depend on net/mail.
  • Identify endpoints or workers parsing user-controlled email address data.
  • Confirm build images and distro packages include the vendor fix.
  • Add regression tests with oversized pathological email-address inputs.
  • Monitor CPU saturation and parser latency on mail-processing paths.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-1046: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-407: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-42499 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
18Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-42499Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPnet/mail: golang: net/mail: Denial of Service via pathological email address parsing
other:Red Hat severity ratingcvssV3_1
  • 2026-05-07T20:00:51.685Z: Reported to Red Hat.
  • 2026-05-07T19:41:18.615Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Go standard librarynet/mailnet/mail, 0, 1.26.0-0unaffected
Weakness

CWE details

CWE-1046CWE-407

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1046 · source CWE mapping

Creation of Immutable Text Using String Concatenation

Creation of Immutable Text Using String Concatenation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-407 · source CWE mapping

Inefficient Algorithmic Complexity

Inefficient Algorithmic Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs