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ExploitedIn CISA KEVFix available

CVE-2016-10033

Exploitation confirmed. First attested on 2025-07-07 by CISA-ADP, CISA KEV, GCVE · kevintel.

  • Published2016-12-30
  • WeaknessCWE-88

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The mailSend function in the isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted Sender property.

Timeline

dates in UTC
  1. 2016-12-3019:59CVE publishedNVD
  2. 2025-07-07Listed as exploited by GCVEGCVE
  3. 2025-07-07Exploitation first reportedCISA KEV
  4. 2025-07-07Added to the CISA KEV catalogCISA KEV
  5. 2025-07-1703:55SSVC exploitation set to activeCISA-ADP
  6. 2026-10-2319:23First public proof of conceptPoC-in-GitHub
  7. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2016-10033?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2016-10033?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Joomla
BranchAffectedFixed in
3.6≥ 1.5.0, ≤ 3.6.5no fix published
Phpmailer project phpmailer
BranchAffectedFixed in
5.2< 5.2.185.2.18
WordPress
BranchAffectedFixed in
4.7≤ 4.7no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. CISA’s required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.due 2025-07-28

Advisories and patches

Detection

read 2026-10-23 19:23 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
17 repositories, unverifiedopsxcq/exploit-CVE-2016-10033Zenexer/safeshellGeneralTesler/CVE-2016-10033chipironcin/CVE-2016-10033Bajunan/CVE-2016-10033
PoC-in-GitHub

CISA Known Exploited Vulnerability

Date Added
2025-07-07
Patch Due Date
2025-07-28
Ransomware Use
Unknown
Required Action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2016-12-30
Last Modified
2026-06-17
NVD status
Analyzed

Frequently asked questions

What is CVE-2016-10033?

The mailSend function in the isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted Sender property.

Is CVE-2016-10033 actively exploited?

Yes. CVE-2016-10033 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2025-07-28.

What is the CVSS score for CVE-2016-10033?

CVE-2016-10033 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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