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CVE-2025-39946 Critical

tls: make sure to abort the stream if headers are bogus

In the Linux kernel, the following vulnerability has been resolved: tls: make sure to abort the stream if headers are bogus Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffer, however, we read out the data sooner, to prevent connection stalls. Make sure that we abort the connection when we find out late that the record is actually invalid. Retrying the parsing is fine in itself but since we copy some more data each time before we parse we can overflow the allocated skb space. Constructing a scenario in which we're under pressure without enough data in the socket to parse the length upfront is quite hard. syzbot figured out a way to do this by serving us the header in small OOB sends, and then filling in the recvbuf with a large normal send. Make sure that tls_rx_msg_size() aborts strp, if we reach an invalid record there's really no way to recover.

Exploit probability 8.9%
Published October 4, 2025
Required by Not available
Last source change July 15, 2026

02 / AFFECTED SOFTWARE

Affected packages

Android :linux_kernel:

1 explicit affected versions

Android :linux_kernel:

1 explicit affected versions

Linux Kernel
Unknown Unknown

03 / CONNECTIONS

Connected vulnerabilities

related OPENSUSE-SU-2025:20081-1
related SUSE-SU-2025:21040-1
related SUSE-SU-2025:21052-1
related SUSE-SU-2025:21056-1
related SUSE-SU-2025:21064-1
related SUSE-SU-2025:21074-1
related SUSE-SU-2025:21139-1
related SUSE-SU-2025:21179-1
related SUSE-SU-2025:4057-1
related SUSE-SU-2025:4128-1
related SUSE-SU-2025:4132-1
related SUSE-SU-2025:4140-1
related SUSE-SU-2025:4141-1
related SUSE-SU-2025:4301-1

04 / EVIDENCE

Source records

Open Source Vulnerabilities ASB-A-432728472

In tls_rx_msg_size of tls_sw.c, there is a possible out of bounds write due to an incorrect bounds check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.

View original source
Open Source Vulnerabilities ASB-A-446648770

In multiple locations, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.

View original source
Open Source Vulnerabilities CVE-2025-39946

In the Linux kernel, the following vulnerability has been resolved: tls: make sure to abort the stream if headers are bogus Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffer, however, we read out the data sooner, to prevent connection stalls. Make sure that we abort the connection when we find out late that the record is actually invalid. Retrying the parsing is fine in itself but since we copy some more data each time before we parse we can overflow the allocated skb space. Constructing a scenario in which we're under pressure without enough data in the socket to parse the length upfront is quite hard. syzbot figured out a way to do this by serving us the header in small OOB sends, and then filling in the recvbuf with a large normal send. Make sure that tls_rx_msg_size() aborts strp, if we reach an invalid record there's really no way to recover.

View original source

05 / REFERENCES

Further evidence