CVE-2026-40686Disclosure(exim / exim)

LOWCVSS 5.3 · MEDIUM

Signal is active with 1 mentions in latest observed window

Immediate actions

Patch exim exim systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD 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.

exim CVEs Back to dashboard

0.5/ 10 priority

Sources & remediation

Patch / fix

https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc

Vendor / third-party advisories

Other references

https://exim.org/static/doc/security/CVE-2026-40686.txt

Weakness type (CWE)

CWE-125

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

exim

Threat summary

Patch or workaround signal is available
5 mentions across 3 observed days
Momentum state: stable

What's happening

Patch or workaround mentioned in 2 signals
Technical details provided in 5 signals
Disclosure: 3 classified signals
Peaked 2d ago at 3 mentions (2026-04-30); latest day: 1
5 total mentions across 3 days

Affected systems

Vendors

exim

Products

exim

Deep dive

Activity timeline5 mentions / 3d

Signal classification2 categories

Disclosure

360.0%

Patch

240.0%

Referenced assets4 URLs

By indicator

Classification over time

Date	Total	Labels

2026-04-30	3	Disclosure2Patch1
2026-05-01	1	Disclosure1
2026-05-05	1	Patch1

Full discourse5 posts

Open Source Security mailing list@oss_security161d
Patch
Exim 4.99.2 fixes https://www.openwall.com/lists/oss-security/2026/04/30/21 CVE-2026-40684: Crash with malicious DNS data when using musl libc CVE-2026-40685: OOB read/write on corrupt JSON in header CVE-2026-40686: OOB read with large UTF8 trailing characters CVE-2026-40687: OOB read/write with SPA authenticator
Post summary
Exim 4.99.2 released a patch that addresses four CVEs involving crashes and out‑of‑bounds memory issues.
02080453
4.7K followersView on X
CVE@CVEnew161d
Disclosure
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). I… https://www.cve.org/CVERecord?id=CVE-2026-40686
Post summary
The text announces CVE‑2026‑40686 in Exim, outlining an out‑of‑bounds read triggered by malformed UTF‑8 header data in versions prior to 4.99.2; no PoC, exploit, or patch is mentioned.
00010144
57.4K followersView on X
Samet Geranaz@sametgeranaz156d
Patch
cPanel biraz önce yeni bir güvenlik zaafiyeti bildirdi. Exim'de, 4.99.2 öncesi sürümleri etkileyen güvenlik açıkları var. Exim CVE-2026-40684, CVE-2026-40685, CVE-2026-40686 ve CVE-2026-40687. Acilen cPanel güncellemesi yapın! #cpanel #hack #security
Post summary
cPanel reports multiple CVEs (CVE‑2026‑40684–40687) affecting Exim versions prior to 4.99.2 and urges users to apply updates.
0000078
465 followersView on X
Vulmon Vulnerability Feed@VulmonFeeds161d
Disclosure
CVE-2026-40686 Out-of-Bounds Read in Exim Before 4.99.2 With UTF-8 Operators Enabled https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-40686
Post summary
The text refers to CVE‑2026‑40686, describing an out‑of‑bounds read vulnerability in Exim versions before 4.99.2 when UTF‑8 operators are enabled, but it does not provide PoC, exploit code, active exploitation evidence, or a patch.
0000034
4.0K followersView on X
Infoflowcloud@infoflowcloud161d
Disclosure
🚨*CVE* 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). I… https://www.cve.org/CVERecord?id=CVE-2026-40686 ----- Traducción: CVE-2026-40686 En … http://infoflow.cloud`
Post summary
This post announces CVE-2026-40686, noting that Exim versions before 4.99.2 with UTF‑8 operators enabled suffer an out‑of‑bounds read when large malformed UTF‑8 trailing characters are present.
0000018
75 followersView on X

CPE platform detail1 entries

Part:

Vendor:

Product:

Version:

Target SW:

Target HW:

1 of 1 entries

Part	Vendor	Product	Version	Target SW	Target HW
App	exim	exim	-	-	-

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What researchers are saying

CVE-2026-40686

Open Source Security mailing list@oss_securityPatch

Exim 4.99.2 released a patch that addresses four CVEs involving crashes and out‑of‑bounds memory issues.

CVE@CVEnewDisclosure

The text announces CVE‑2026‑40686 in Exim, outlining an out‑of‑bounds read triggered by malformed UTF‑8 header data in versions prior to 4.99.2; no PoC, exploit, or patch is mentioned.

Samet Geranaz@sametgeranazPatch

cPanel reports multiple CVEs (CVE‑2026‑40684–40687) affecting Exim versions prior to 4.99.2 and urges users to apply updates.

Vulmon Vulnerability Feed@VulmonFeedsDisclosure

The text refers to CVE‑2026‑40686, describing an out‑of‑bounds read vulnerability in Exim versions before 4.99.2 when UTF‑8 operators are enabled, but it does not provide PoC, exploit code, active exploitation evidence, or a patch.

Infoflowcloud@infoflowcloudDisclosure

This post announces CVE-2026-40686, noting that Exim versions before 4.99.2 with UTF‑8 operators enabled suffer an out‑of‑bounds read when large malformed UTF‑8 trailing characters are present.