What’s Vulnerable › Vulnerabilities

CVE-2026-90088: Bluetooth: RFCOMM: Validate MTU in rfcomm_apply_pn() to prevent infinite loop

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: RFCOMM: Validate MTU in rfcomm_apply_pn() to prevent infinite loop rfcomm_apply_pn() accepts the MTU value from a remote PN (Parameter Negotiation) frame without checking for zero. When the remote peer sends an MTU of zero, d->mtu is set to 0. This causes the sendmsg path to enter an infinite loop when fragmenting data, as each fragment has size == min_t(size_t, len, 0) == 0, so the remaining length never decreases. The infinite allocation of zero-length skbs exhausts all system memory. Fix by clamping d->mtu to RFCOMM_DEFAULT_MTU when the negotiated value is zero, consistent with the initial value assigned in rfcomm_dlc_alloc().

Affected products

• Linux kernel: 2.6.12 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/3988cbb1be501dbff909a2ee024670e3c955a66d
• https://git.kernel.org/stable/c/44c98fd082eafd49d55a8a4077ff488175b2fe24
• https://git.kernel.org/stable/c/9b2e5f1928c99224345a9ed8c5dae5fc74964d6d
• https://git.kernel.org/stable/c/aeee917a4878af95f0c63e18c5f22eaf6299c7b8
• https://git.kernel.org/stable/c/cbc2962da99b6b89345267d3aa74b4b573340548
• https://git.kernel.org/stable/c/e7c0aa45ae6c5a338661b23812bfcdef50bf3e96
• https://git.kernel.org/stable/c/f561e44261344adadf9d6a6dff31e3af9776d5c6
• https://git.kernel.org/stable/c/fc4851ff8dfb505e9a19efcc286712132bbd178d

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