CVE-2022-3620Network attack vector

Remote memory corruption via premature DNS answer free

Published Oct 20, 2022 · Updated Apr 15, 2025

Use-after-free in Exim's DMARC handler allows remote attackers to trigger invalid memory access while DMARC DNS results are processed. In dmarc_dns_lookup in dmarc.c, the code frees the dns_lookup answer before copying a TXT record from the freed rr->data buffer. Exposure requires a build with SUPPORT_DMARC and can corrupt memory or crash the mail-handling process.

CVSS severity9.8
Critical
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in Exim's DMARC handler allows remote attackers to trigger invalid memory access while DMARC DNS results are processed. In dmarc_dns_lookup in dmarc.c, the code frees the dns_lookup answer before copying a TXT record from the freed rr->data buffer. Exposure requires a build with SUPPORT_DMARC and can corrupt memory or crash the mail-handling process.

The record

CVE
CVE-2022-3620
Published
Oct 20, 2022
Updated
Apr 15, 2025
Vendor
LibSPF2 Project
Product
Exim
Classifications
CWE-416, CWE-119, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LibSPF2 Project · Eximversion=n/a

Published CVSS scores

9.8National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo