CVE-2026-67306: Out-of-bounds Read (CVSS 5.4)

Description

FreeRDP versions 3.28.0 and earlier contain an out-of-bounds read vulnerability in the RDP6 planar RLE bitmap decoder functions planar_decompress_plane_rle and planar_decompress_plane_rle_only in libfreerdp/codec/planar.c. Only the 1-byte control byte is bounds-checked; the subsequent 0–15 attacker-declared raw bytes are read without validating that the source buffer contains them. A malicious or compromised RDP server can send a truncated planar-encoded bitmap or surface update (reachable via both the Bitmap Update PDU and RDPGFX Surface Command paths) that causes the client to read past the end of the source buffer. The issue is fixed in FreeRDP 3.29.0.

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CVSS v3.1 Score

5.4

MEDIUM

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

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.20%

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-125 Out-of-bounds Read

References

Other References

https://github.com/FreeRDP/FreeRDP/commit/5370fb26fbf034ecd11d3026b6ad639b5fff493f https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-qrxx-7g3c-j6w3 https://www.vulncheck.com/advisories/freerdp-before-out-of-bounds-read-via-planar-rle https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-qrxx-7g3c-j6w3

Frequently Asked Questions

What is CVE-2026-67306? +

FreeRDP versions 3.28.0 and earlier contain an out-of-bounds read vulnerability in the RDP6 planar RLE bitmap decoder functions planar_decompress_plane_rle and planar_decompress_plane_rle_only in libfreerdp/codec/planar.c. Only the 1-byte control byte is bounds-checked; the subsequent 0–15 attacker-declared raw bytes are read without validating that the source buffer contains them. A malicious or compromised RDP server can send a truncated planar-encoded bitmap or surface update (reachable via both the Bitmap Update PDU and RDPGFX Surface Command paths) that causes the client to read past the end of the source buffer. The issue is fixed in FreeRDP 3.29.0. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-67306? +

CVE-2026-67306 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-67306? +

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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