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Mallory
High

DoS in Go net/mail consumePhrase

IdentifiersCVE-2026-42499CWE-400

CVE-2026-42499 is a denial-of-service vulnerability in Go's net/mail package. The issue occurs in consumePhrase while parsing email addresses according to RFC 5322. Pathological crafted inputs can trigger excessive processing due to quadratic string concatenation behavior during phrase parsing, allowing an attacker to cause disproportionate resource consumption when the application parses attacker-controlled email address data.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause denial of service by driving excessive CPU consumption during RFC 5322 email address parsing in applications that rely on the vulnerable net/mail functionality. Depending on how the parser is exposed, this may degrade performance, tie up worker resources, or make the service unavailable.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, reduce exposure by avoiding direct parsing of untrusted email address inputs with the vulnerable net/mail code path, enforcing strict input size and complexity limits on email header/address fields, applying request rate limiting and resource controls, and isolating parsing workloads so malformed inputs cannot exhaust shared service capacity. These are compensating controls; the primary fix is upgrading Go.

Remediation

Patch, then assume compromise.

Upgrade to a fixed Go release that includes the net/mail correction for CVE-2026-42499. The provided context indicates the issue was addressed in Go 1.26.3 and Go 1.25.10 as part of the May 8, 2026 security releases.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

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GolangGoapplication

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Threat actor evidence

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Associated malware

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Detection signatures

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Social activity10

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