CVE-2021-31986Network attack vector

Device crash and data disclosure via SMTP overflow

Published Oct 5, 2021 · Updated Nov 8, 2024

Heap-based buffer overflow in AXIS OS 6.40 and later allows remote attackers to crash devices or disclose data through SMTP tests. The libhttp_smtp_notify.so read callback copies externally controlled to, from, subject, and body parameters from /axis-cgi/smtptest.cgi into libcurl's destination buffer without enforcing the size-times-items limit. Exploitation requires network and administrator access, or interaction from an administrator logged into the device; impact is bounded to a device crash and data disclosure.

CVSS severity6.8
Medium
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

Heap-based buffer overflow in AXIS OS 6.40 and later allows remote attackers to crash devices or disclose data through SMTP tests. The libhttp_smtp_notify.so read callback copies externally controlled to, from, subject, and body parameters from /axis-cgi/smtptest.cgi into libcurl's destination buffer without enforcing the size-times-items limit. Exploitation requires network and administrator access, or interaction from an administrator logged into the device; impact is bounded to a device crash and data disclosure.

The record

CVE
CVE-2021-31986
Published
Oct 5, 2021
Updated
Nov 8, 2024
Vendor
Axis Communications AB
Product
AXIS OS
Classifications
CWE-787, CWE-122
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Oct 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 2024Record 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=AXIS OS 6.40 or later

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Axis Communications AB · AXIS OSversion=AXIS OS 6.40 or later

Published CVSS scores

6.8NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:H
4.0NIST NVDAV:N/AC:H/Au:N/C:P/I:N/A:P

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-122Heap-based Buffer Overflow

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