How severe is CVE-2026-40685?

CVE-2026-40685 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.

Is CVE-2026-40685 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40685?

CVE-2026-40685 affects Exim. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40685?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40685 have an EU (EUVD) identifier?

Yes. CVE-2026-40685 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26443.

When was CVE-2026-40685 published?

CVE-2026-40685 was published on 2026-04-30 and last updated on 2026-06-17.

CVE-2026-40685

CVE-2026-40685 is a medium-severity vulnerability in Exim with a CVSS 3.x base score of 6.5. 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-787.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (24th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-26443
Weakness: CWE-787
Affected product: Exim
Published: 2026-04-30
Last modified: 2026-06-17

Description

In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.

Frequently asked questions

What is CVE-2026-40685?: In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.
How severe is CVE-2026-40685?: CVE-2026-40685 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.
Is CVE-2026-40685 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40685?: CVE-2026-40685 affects Exim. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40685?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40685 have an EU (EUVD) identifier?: Yes. CVE-2026-40685 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26443.
When was CVE-2026-40685 published?: CVE-2026-40685 was published on 2026-04-30 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

193.202.11.112 (ipv4-addr)
76.12.128.249 (ipv4-addr)
50.116.72.139 (ipv4-addr)
166.62.41.190 (ipv4-addr)
160.187.147.124 (ipv4-addr)
132.148.155.138 (ipv4-addr)
77.221.151.241 (ipv4-addr)
37.221.254.200 (ipv4-addr)