CVE-2023-42118: Exim libspf2 Integer Underflow Remote Code Execution Vulnerability

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HIGH 8.8MITIGATE

CVE-2023-42118 is a high-severity flaw (CVSS 8.8) affecting libspf2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Exim libspf2 Integer Underflow Remote Code Execution Vulnerability. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of Exim libspf2. Authentication is not required to exploit this vulnerability. The specific flaw exists within the parsing of SPF macros. When parsing SPF macros, the process does not properly validate user-supplied data, which can result in an integer underflow before writi

Why this priority

High severity
EPSS top 5%: very likely to be exploited

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.8 (High)
Attack vector	Adjacent network
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	8.4% (top 5%)
CISA exploited list	No
Weakness	CWE-191
Published	2024-05-03
Last modified	2026-06-17

Publisher (CNA): Zero Day Initiative · Vendor: libspf2 project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-05-03 03:15 UTCPublished CVE record published
2026-06-17 06:23 UTCUpdated Record last modified

libspf2 project libspf2 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libspf2 || rpm -q libspf2 || libspf2 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-42118?

libspf2: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-42118 being exploited?

CVE-2023-42118 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-42118 affect?

CVE-2023-42118 affects libspf2. Severity is high (CVSS 8.8). Exim libspf2 Integer Underflow Remote Code Execution Vulnerability. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of Exim libspf2. Authentication is not required to exploit this vul

How urgent is CVE-2023-42118?

Priority 55/100. High severity; EPSS top 5%: very likely to be exploited

Software pages

Exim vulnerabilities

References

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