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CVE-2021-47496

Disclosure Date: May 22, 2024 •
CVE-2021-47496
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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 Severity and Metrics
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Impact Score:
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Exploitability Score:
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Vector:
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Attack Vector (AV):
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Attack Complexity (AC):
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Integrity (I):
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Availability (A):
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General Information

Offensive Application
Unknown
Utility Class
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Ports
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OS
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Vulnerable Versions
Linux e0cfd5159f31
Linux not down converted
Prerequisites
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Discovered By
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PoC Author
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Metasploit Module
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Reporter
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Vendors

  • Linux

Products

  • Linux
Technical Analysis