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CVE-2025-39946 is an out-of-bounds write vulnerability in the Linux kernel TLS receive path. When a socket has a very small receive buffer, TLS processing may parse a record before the complete record is buffered to avoid connection stalls. If an invalid TLS record header is discovered only after partial data has been copied, repeated parsing attempts copy further data before each attempt and can overflow the allocated socket-buffer (skb) space. The flaw is corrected by aborting the stream parser from tls_rx_msg_size() when an invalid TLS record is encountered.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository contains a working exploit for CVE-2025-39946, targeting the Linux kernel version lts-6.12.48, specifically in a kCTF (Kubernetes Capture The Flag) environment. The exploit is implemented in a single C file ('exploit.c'), which is compiled statically via a simple Makefile. The README provides context, usage notes, and adaptation instructions for other kernel versions (primarily requiring adjustment of the 'CORE_PATTERN_OFFSET'). The exploit leverages advanced kernel memory manipulation techniques, including socket and page table spraying, to achieve privilege escalation or arbitrary file read. Upon successful exploitation, the payload reads and prints the contents of '/flag' to stdout, which is typical for CTF challenges. It also interacts with '/proc/sysrq-trigger' as a side effect. The exploit requires the ability to open a large number of file descriptors and is tailored for a specific kernel version, but can be adapted for others with minor changes. No network endpoints are targeted beyond local loopback sockets used for memory manipulation. The code demonstrates a high level of sophistication and is operational, though not weaponized for broad use.
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27 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel TLS receive-path flaw in which invalid TLS records can cause repeated parsing and additional copying, potentially overflowing allocated socket-buffer (skb) space. It affects Google COS packages sys-kernel/csql-kernel-6_1 and sys-kernel/lakitu-kernel-6_1 before version 18244.448.58.
A Linux kernel TLS receive-path memory-overflow vulnerability. Malformed TLS record handling could cause repeated parsing and copying into allocated skb space until it overflows; the fix aborts the stream upon detecting an invalid record.
A Linux kernel TLS issue involving handling of bogus headers; the fix ensures the stream is aborted. Red Hat included the fix in its Moderate-severity kernel update for Red Hat Enterprise Linux 10.
Unknown
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