CVE-2026-43964Network attack vector

Process crash via enhanced-status-code pointer overadvance

Published May 4, 2026 · Updated May 4, 2026

Off-by-one error in Postfix 2.3 through 3.8.15, 3.9 through 3.9.9, and 3.10 through 3.10.8 allows remote attackers to crash a process. The enhanced-status-code parser in dsn_util.c advances its pointer one byte beyond the code terminator when no following text exists, causing a buffer over-read. Reachability requires an uncommon input path such as an access table, policy response, or configured DNSBL TXT reply; SMTP and LMTP server responses cannot trigger it.

CVSS severity3.7
Low
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Off-by-one error in Postfix 2.3 through 3.8.15, 3.9 through 3.9.9, and 3.10 through 3.10.8 allows remote attackers to crash a process. The enhanced-status-code parser in dsn_util.c advances its pointer one byte beyond the code terminator when no following text exists, causing a buffer over-read. Reachability requires an uncommon input path such as an access table, policy response, or configured DNSBL TXT reply; SMTP and LMTP server responses cannot trigger it.

The record

CVE
CVE-2026-43964
Published
May 4, 2026
Updated
May 4, 2026
Vendor
Postfix
Product
Postfix
Classifications
CWE-193, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 4, 2026CVE publishedPublication date reported by the CVE source.
  2. May 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=2.3 <3.8.16
  2. Affected versionversion=3.10 <3.10.9
  3. Affected versionversion=3.9 <3.9.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Postfix · Postfixversion=2.3 <3.8.16; version=3.10 <3.10.9; version=3.9 <3.9.10

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.7MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-193Off-by-one Error
T1499.004Application or System Exploitation

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

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Your stack

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