9.8
CRITICAL CVSS 3.1
CVE-2026-63979
net/handshake: hand off the pinned file reference to accept_doit
Description

In the Linux kernel, the following vulnerability has been resolved: net/handshake: hand off the pinned file reference to accept_doit handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()). In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory. The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected. Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file. Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the !remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference. Hand off an additional file reference inside handshake_req_next(), under hn_lock, so the accept side operates on a reference that no concurrent handshake_req_cancel() can revoke. FD_PREPARE() consumes that handed-off reference, either by transferring it to the new fd in fd_publish() or by dropping it in the cleanup destructor on error; the explicit get_file() that previously balanced FD_PREPARE() is therefore redundant and goes away. Update handshake_req_cancel_test2 and _test3 to simulate the FD_PREPARE() consumption with an fput() so the kunit file-count assertions stay balanced.

INFO

Published Date :

July 19, 2026, 4:17 p.m.

Last Modified :

Aug. 9, 2026, 7:17 p.m.

Remotely Exploit :

Yes !

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products

The following products are affected by CVE-2026-63979 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Linux linux_kernel
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 CRITICAL 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
Resolve race condition by retargeting dereferences to a pinned file reference.
  • Retarget accept-side dereferences to req->hr_file.
  • Pin the file reference at submit time.
  • Hand off an additional file reference under hn_lock.
  • Update tests to simulate FD_PREPARE() consumption.
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-63979.

URL Resource
https://git.kernel.org/stable/c/68eba6519cbd6359fb554a9720f3a3b6b2eba23f
https://git.kernel.org/stable/c/c06876d4fac38f35820946ee3b1be7d7da799cd4
https://git.kernel.org/stable/c/f4251190e58b209999c1ba9e6d2976136a1be055
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-63979 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-63979 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-63979 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2026-63979 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Aug. 09, 2026

    Action Type Old Value New Value
    Added Reference https://git.kernel.org/stable/c/68eba6519cbd6359fb554a9720f3a3b6b2eba23f
    Changed Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'c06876d4fac38f35820946ee3b1be7d7da799cd4', 'versionType': 'git'}, {'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'f4251190e58b209999c1ba9e6d2976136a1be055', 'versionType': 'git'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.4'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.4', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'affected'}] [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': '68eba6519cbd6359fb554a9720f3a3b6b2eba23f', 'versionType': 'git'}, {'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'c06876d4fac38f35820946ee3b1be7d7da799cd4', 'versionType': 'git'}, {'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'f4251190e58b209999c1ba9e6d2976136a1be055', 'versionType': 'git'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.4'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.4', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.18.44', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'affected'}]
  • CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Jul. 20, 2026

    Action Type Old Value New Value
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Jul. 19, 2026

    Action Type Old Value New Value
    Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'c06876d4fac38f35820946ee3b1be7d7da799cd4', 'versionType': 'git'}, {'status': 'affected', 'version': '3b3009ea8abb713b022d94fba95ec270cf6e7eae', 'lessThan': 'f4251190e58b209999c1ba9e6d2976136a1be055', 'versionType': 'git'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.4'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.4', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/handshake/handshake-test.c', 'net/handshake/netlink.c', 'net/handshake/request.c'], 'defaultStatus': 'affected'}]
    Added Description In the Linux kernel, the following vulnerability has been resolved: net/handshake: hand off the pinned file reference to accept_doit handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()). In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory. The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected. Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file. Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the !remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference. Hand off an additional file reference inside handshake_req_next(), under hn_lock, so the accept side operates on a reference that no concurrent handshake_req_cancel() can revoke. FD_PREPARE() consumes that handed-off reference, either by transferring it to the new fd in fd_publish() or by dropping it in the cleanup destructor on error; the explicit get_file() that previously balanced FD_PREPARE() is therefore redundant and goes away. Update handshake_req_cancel_test2 and _test3 to simulate the FD_PREPARE() consumption with an fput() so the kunit file-count assertions stay balanced.
    Added Reference https://git.kernel.org/stable/c/c06876d4fac38f35820946ee3b1be7d7da799cd4
    Added Reference https://git.kernel.org/stable/c/f4251190e58b209999c1ba9e6d2976136a1be055
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.