CVE-2021-47496: linux kernel Memory Corruption — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: net/tls: Fix flipped sign in tls_err_abort() calls sk->sk_err appears to expect a positive value, a convention that ktls doesn't always follow and that leads to memory corruption in other code. For instance, [kworker] tls_encrypt_done(..., err=<negative error from crypto request>) tls_err_abort(.., err) sk->sk_err = err; [task] splice_from_pipe_feed ... tls_sw_do_sendpage if (sk->sk_err) { ret = -sk->sk_err; // ret is positive splice_from_pipe_feed (continued) ret = actor(...) // ret is still positive and interpreted as bytes // written, resulting in underflow of buf->len and // sd->len, leading to huge buf->offset and bogus // addresses computed in later calls to actor() Fix all tls_err_abort() callers to pass a negative error code consistently and centralize the error-prone sign flip there, throwing in a warning to catch future misuse and uninlining the function so it really does only warn once.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.17 — 5.4.157
linux	linux_kernel	5.5 — 5.10.77
linux	linux_kernel	5.11 — 5.14.16
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/da353fac65fede6b8b4cfe207f0d9408e3121105 https://git.kernel.org/stable/c/e0cfd5159f314d6b304d030363650b06a2299cbb https://git.kernel.org/stable/c/e41473543f75f7dbc5d605007e6f883f1bd13b9a https://git.kernel.org/stable/c/f3dec7e7ace38224f82cf83f0049159d067c2e19 https://git.kernel.org/stable/c/da353fac65fede6b8b4cfe207f0d9408e3121105 https://git.kernel.org/stable/c/e0cfd5159f314d6b304d030363650b06a2299cbb https://git.kernel.org/stable/c/e41473543f75f7dbc5d605007e6f883f1bd13b9a https://git.kernel.org/stable/c/f3dec7e7ace38224f82cf83f0049159d067c2e19

Frequently Asked Questions

What is CVE-2021-47496? +

In the Linux kernel, the following vulnerability has been resolved: net/tls: Fix flipped sign in tls_err_abort() calls sk->sk_err appears to expect a positive value, a convention that ktls doesn't always follow and that leads to memory corruption in other code. For instance, [kworker] tls_encrypt_done(..., err=<negative error from crypto request>) tls_err_abort(.., err) sk->sk_err = err; [task] splice_from_pipe_feed ... tls_sw_do_sendpage if (sk->sk_err) { ret = -sk->sk_err; // ret is positive splice_from_pipe_feed (continued) ret = actor(...) // ret is still positive and interpreted as bytes // written, resulting in underflow of buf->len and // sd->len, leading to huge buf->offset and bogus // addresses computed in later calls to actor() Fix all tls_err_abort() callers to pass a negative error code consistently and centralize the error-prone sign flip there, throwing in a warning to catch future misuse and uninlining the function so it really does only warn once. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47496? +

CVE-2021-47496 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2021-47496? +

CVE-2021-47496 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47496? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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