CVE-2026-42504 | Quadratic complexity in WordDecoder.DecodeHeader in mime

Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.

Published: 2026-06-02 Last update: 2026-06-04 Assigner: [email protected] Source: [email protected]
NVD Status：Awaiting Analysis，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-42504 is rated Moderate Risk (40.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.38%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-42504

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 0.38% +0.33%
2 2026-06-08 0.02% 0.06% +0.04%
3 2026-06-03 — 0.02% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-42504

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-42504

GitHub Security Advisory for CVE-2026-42504

GHSA-h524-452v-82p9 · Severity: high — Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume...

OS Trackers for CVE-2026-42504

vendor priority summary link
debian not yet assigned CVE-2026-42504 not yet assigned priority: Debian including 5 source packages (golang-1.15, golang-1.19, golang-1.24, golang-1.25, golang-1.26), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 3. https://security-tracker.debian.org/tracker/CVE-2026-42504
suse medium CVE-2026-42504 severity moderate: SUSE including 3 source package names (go, go-doc, go-race), 30 product×package rows across 14 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (14 product lines)): Known Not Affected 30. https://www.suse.com/security/cve/CVE-2026-42504/
ubuntu medium CVE-2026-42504 medium priority: Ubuntu including 3 source packages (golang-1.24, golang-1.25, golang-1.26), 15 status rows across 5 suites (jammy, noble, questing, resolute, upstream): needs-triage 10, DNE 5. https://ubuntu.com/security/CVE-2026-42504

Affected software / configurations for CVE-2026-42504

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-42504

cvelogic Threat Intelligence