CVE-2026-84267: Gvfs: sftp: uninitialized heap disclosure in read_string()

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-01 · updated 2026-09-02
Weakness: CWE-908

Description

A flaw was found in the SFTP backend in gvfs. When mounting a share, a malicious SFTP server can cause read_string() to allocate a buffer with a certain length but the function does not verify that the buffer is completely filled, leaving the remainder of the buffer containing uninitialized heap contents. If the server sends a short FXP_HANDLE reply, these uninitialized bytes are taken as the file handle. The client will then echo these uninitialized bytes back to the server on all subsequent requests using that handle. With a length of 128 bytes, this issue allows the malicious server to deterministically read uninitialized heap memory from the gvfsd-sftp process, leaking its heap base and the load address of the libgio library, resulting in a deterministic defeat of Address Space Layout Randomization (ASLR).

Affected products

GNOME gvfs: from 1.10.0 before 1.60.2 — fixed in 1.60.2
Red Hat Enterprise Linux 10: all versions
Red Hat Enterprise Linux 7: all versions
Red Hat Enterprise Linux 8: all versions
Red Hat Enterprise Linux 9: all versions

How to fix

Upgrade to a fixed version: GNOME gvfs 1.60.2. Check the vendor advisory for mitigations.

References

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