CVE-2021-47496 net/tls: Fix flipped sign in tls_err_abort() calls
A sign error in Linux kernel TLS handling causes memory corruption, potentially allowing attackers to execute arbitrary code or crash the system.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-47496?
CVE-2021-47496 is a critical memory corruption vulnerability in Linux kernel, published on 22 May 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2021-47496?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-47496?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2021-47496 being exploited?
There is no known exploitation of CVE-2021-47496 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2021-47496, GHSA-c425-5ghg-6j48, UBUNTU-CVE-2021-47496.