Out-of-Bounds Heap Read in libslirp on Freedesktop.org Affects Multiple Hypervisor Environments

CVE-2026-9539

What is CVE-2026-9539?

An out-of-bounds heap read and integer underflow vulnerability exists in the TCP urgent data handling mechanism of the libslirp library on freedesktop.org. This issue affects hypervisor host environments such as QEMU and allows a privileged guest VM attacker to exploit the vulnerability. By sending specially crafted TCP segments with altered URG flags and urgent pointers, the attacker can leak significant amounts of sensitive heap memory from the host process, potentially compromising data integrity and confidentiality. Users are encouraged to update to libslirp version 4.9.2 or later to mitigate this risk.

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