How severe is CVE-2026-42504?

CVE-2026-42504 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42504 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-42504?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42504 have an EU (EUVD) identifier?

Yes. CVE-2026-42504 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34039.

When was CVE-2026-42504 published?

CVE-2026-42504 was published on 2026-06-02 and last updated on 2026-07-22.

CVE-2026-42504

CVE-2026-42504 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-407.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-34039
Weakness: CWE-407
Published: 2026-06-02
Last modified: 2026-07-22

Description

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

Frequently asked questions

What is CVE-2026-42504?: Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.
How severe is CVE-2026-42504?: CVE-2026-42504 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42504 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-42504?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42504 have an EU (EUVD) identifier?: Yes. CVE-2026-42504 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34039.
When was CVE-2026-42504 published?: CVE-2026-42504 was published on 2026-06-02 and last updated on 2026-07-22.

References

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