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Fencer Vulns
medium 4.3

CVE-2026-55696 json

PrivateBin: Stored Cross-Side-Scripting (XSS) vulnerability in attachment download link via dangerous MIME types with required user-interaction

published 2026-08-28 2 mo ago modified 2026-09-09 1 mo ago also GHSA-f2xf-7x3g-4272 , EUVD-2026-67938

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

PrivateBin is an online pastebin where the server has zero knowledge of pasted data. Prior to 2.0.5, AttachmentViewer.setAttachment in js/privatebin.js uses getAttachmentMimeType to accept attacker-controlled MIME types and uses getBlobUrl to create a same-origin blob before setting attachmentLink's href for the Download attachment link. The SVG-only sanitization branch updates only the preview blob, so text/html, image/svg, application/xhtml+xml, and text/xml attachments can remain active in the download blob. On an instance with fileupload = true and a weakened, stripped, or absent Content Security Policy, an anonymous attacker can create such an attachment, and a victim who opens the link in a new tab causes inline JavaScript to execute in the PrivateBin origin. The script can read origin-scoped local storage and issue same-origin requests, including requests to applications co-hosted on the same domain. This issue is fixed in version 2.0.5.

Patch / fix

  • packagist privatebin/privatebin 2.0.5

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
packagist privatebin/privatebin
<2.0.5
2.0.5

Affected products

  • PrivateBin PrivateBin

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.