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CVE-2026-21878

25
FAUCET Score

CVE-2026-21878 is a path traversal vulnerability in the BACnet Stack C library, affecting versions prior to 1.5.0.rc3. This flaw allows an unauthenticated attacker to write files to arbitrary directories due to a lack of validation on user-provided file paths. With a CVSS score of 7.5 (High), this vulnerability has a low attack complexity and can lead to high integrity impact, though confidentiality and availability are not affected. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
1.5.0CPE matchmatch criteria
cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc1:*:*:*:*:*:*
1.5.0CPE matchmatch criteria
cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc2:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.36%
Probability of exploitation in next 30 days
EPSS Percentile
28.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0036 is in the 9th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / bacnet-stack/bacnet-stack/commit/c5dc00a77b4bc2550befa67a930b333e299c18f3
Patch
github.com / bacnet-stack/bacnet-stack/security/advisories/GHSA-p8rx-c26w-545j
ExploitVendor Advisory