CVE-2026-91948: Integer Underflow (CVSS 7.5)

Description

FreeRDP versions before 3.31.0 contain an out-of-bounds write vulnerability in server-side static virtual channel handling when CHANNEL_OPTION_SHOW_PROTOCOL is enabled. Authenticated clients can queue oversized channel messages that cause buffer underflow and corrupt heap memory including live pointers, potentially enabling code execution.

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CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0065

Probability of exploitation

0.49%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-191 CWE-191

References

Other References

https://github.com/FreeRDP/FreeRDP/commit/40d9202cd95551600c07437ce6bd5ecd7d31e57b https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-9jcm-x588-gh26 https://www.vulncheck.com/advisories/freerdp-before-3.31.0-out-of-bounds-write-via-show-protocol https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-9jcm-x588-gh26

Frequently Asked Questions

What is CVE-2026-91948? +

FreeRDP versions before 3.31.0 contain an out-of-bounds write vulnerability in server-side static virtual channel handling when CHANNEL_OPTION_SHOW_PROTOCOL is enabled. Authenticated clients can queue oversized channel messages that cause buffer underflow and corrupt heap memory including live pointers, potentially enabling code execution. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-91948? +

CVE-2026-91948 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0065, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-91948? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-91948