No exploitation reportedFix available

CVE-2021-25978

Q: Is CVE-2021-25978 actively exploited?

Active exploitation of CVE-2021-25978 has not been confirmed. Its EPSS score was 0.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-25978?

CVE-2021-25978 has a CVSS v3 base score of 5.4 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

No exploitation reported by the sources we read.

Published2021-11-07
Fixed in3.4.0
WeaknessCWE-79

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

Apostrophe CMS versions between 2.63.0 to 3.3.1 are vulnerable to Stored XSS where an editor uploads an SVG file that contains malicious JavaScript onto the Images module, which triggers XSS once viewed.

Timeline

dates in UTC

2021-11-0718:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 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-2021-25978?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-25978?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

OSV · NVD

apostrophe

Branch	Affected	Fixed in	Source
3.4	≥ 2.63.0, < 3.4.0	3.4.0	OSV

Apostrophecms

Branch	Affected	Fixed in	Source
3.3	≥ 2.63.0, ≤ 3.3.1	no fix published	NVD

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

Fix

Update apostrophe to 3.4.0

Advisories and patches

github.comPatch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2025-04-30
OpenCVESSVC decisionnone—
CNACVSS 3.15.4read 2026-10-23
NVDCVSS 3.15.4read 2026-10-23
NVDCVSS 2.03.5read 2026-10-23
CNAweakness (CWE)CWE-79read 2026-10-23
NVDweakness (CWE)CWE-79read 2026-10-23
FIRST EPSSEPSS score0.5 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Published: 2021-11-07
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-25978?

Is CVE-2021-25978 actively exploited?

Active exploitation of CVE-2021-25978 has not been confirmed. Its EPSS score was 0.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-25978?

CVE-2021-25978 has a CVSS v3 base score of 5.4 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

Running apostrophe? Hear about its next vulnerability

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

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