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CVE

CVE-2026-78207

exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization
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CVE

CVE-2026-78207

exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization

exceljs through 4.4.0 contains a prototype pollution vulnerability in the deepMerge helper that fails to reject proto, constructor, or prototype keys when merging note objects. Attackers can assign parsed JSON with a malicious proto property to cell notes, modifying Object.prototype and affecting all plain objects created in the process.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9.3
-
4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
9.3
-
4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

Related Resources

No items found.

References

https://www.npmjs.com/package/exceljs, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78207.json, https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-qwr4-7h29-chpf, https://nvd.nist.gov/vuln/detail/CVE-2026-78207, https://www.vulncheck.com/advisories/exceljs-through-prototype-pollution-via-deepmerge-reached-from-note-serialization, https://github.com/exceljs/exceljs, https://github.com/exceljs/exceljs/blob/v4.4.0/lib/utils/under-dash.js#L155-L181

Severity

0

CVSS Score
0
10

Basic Information

Base CVSS
0
EPSS Probability
0.00603%
EPSS Percentile
0.46854%
Introduced Version
0,3.10.0
Fix Available
ac96f9a61e9799c7776bd940f05c4a51d7200209

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