How severe is CVE-2026-40686?

CVE-2026-40686 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2026-40686 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40686?

CVE-2026-40686 affects Exim. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40686?

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

Does CVE-2026-40686 have an EU (EUVD) identifier?

Yes. CVE-2026-40686 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26444.

When was CVE-2026-40686 published?

CVE-2026-40686 was published on 2026-04-30 and last updated on 2026-06-17.

CVE-2026-40686

CVE-2026-40686 is a low-severity vulnerability in Exim with a CVSS 3.x base score of 3.7. 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-125.

Key facts

Severity: Low (CVSS 3.x base score 3.7)
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-26444
Weakness: CWE-125
Affected product: Exim
Published: 2026-04-30
Last modified: 2026-06-17

Description

In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.

Frequently asked questions

What is CVE-2026-40686?: In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
How severe is CVE-2026-40686?: CVE-2026-40686 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2026-40686 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40686?: CVE-2026-40686 affects Exim. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40686?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40686 have an EU (EUVD) identifier?: Yes. CVE-2026-40686 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26444.
When was CVE-2026-40686 published?: CVE-2026-40686 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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Other CWE-125 (Out-of-bounds Read) vulnerabilities

CVE-2026-24826 — Critical (CVSS 10.0): Out-of-bounds Write, Divide By Zero, NULL Pointer Dereference, Use of Uninitialized Resource, Out-of-bounds Read,…
CVE-2024-22004 — Critical (CVSS 10.0): Due to length check, an attacker with privilege access on a Linux Nonsecure operating system can trigger a…
CVE-2021-41556 — Critical (CVSS 10.0): sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that…
CVE-2021-21777 — Critical (CVSS 10.0): An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer…
CVE-2017-14451 — Critical (CVSS 10.0): An exploitable out-of-bounds read vulnerability exists in libevm (Ethereum Virtual Machine) of CPP-Ethereum. A…
CVE-2013-0767 — Critical (CVSS 10.0): The nsSVGPathElement::GetPathLengthScale function in Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and…

Browse all CWE-125 (Out-of-bounds Read) vulnerabilities →

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)