sdcb chats Signed File Download Endpoint FileController.cs DownloadPublic missing authentication

published 2026-08-31 2 mo ago modified 2026-09-01 2 mo ago also EUVD-2026-68763

cvss: 3.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits: 0; none known

A flaw has been found in sdcb chats up to 1.12.0. This impacts the function DownloadPublic of the file src/BE/web/Controllers/Chats/Files/FileController.cs of the component Signed File Download Endpoint. This manipulation causes missing authentication. Remote exploitation of the attack is possible. The attack's complexity is rated as high. The exploitability is said to be difficult. The exploit has been published and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 2 mo ago (2026-09-01)

Exploit prediction

0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/yaowenxiao721/Poc/blob/main/sdcb-chats/chats-poc-2.md referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	6.3	CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
CNA	3.1	3.7	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P/RL:X/RC:R
CNA	3.0	3.7	CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P/RL:X/RC:R
CNA	2.0	2.6	AV:N/AC:H/Au:N/C:P/I:N/A:N/E:POC/RL:ND/RC:UR
CNA	4.0	2.9	CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/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
CNA	3.1	3.7	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CNA	2.0	2.6	AV:N/AC:H/Au:N/C:P/I:N/A:N

Affected products

sdcb chats

Classification

Weakness

CWE-306 Missing Authentication for Critical Functionality
CWE-287 Improper Authentication

References

github.com /yaowenxiao721/Poc/blob/main/sdcb-chats/chats-poc-2.md
exploit
vuldb.com /vuln/397286
vdb-entry, technical-description
vuldb.com /vuln/397286/cti
signature, permissions-required
vuldb.com /cve/CVE-2026-82906
third-party-advisory
vuldb.com /submit/877767
third-party-advisory

Sources

CVE List CVE-2026-82906
NVD CVE-2026-82906

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.

Summary