In affected versions, after a Report is constructed using wrap_err or wrap_err_with to attach a message of type D onto an error of type E, then using downcast to recover ownership of either the value of type D or the value of type E, one of two things can go wrong:

• If downcasting to E, there remains a value of type D to be dropped. It is incorrectly "dropped" by running E's drop behavior, rather than D's. For example if D is &str and E is std::io::Error, there would be a call of std::io::Error::drop in which the reference received by the Drop impl does not refer to a valid value of type std::io::Error, but instead to &str.

• If downcasting to D, there remains a value of type E to be dropped. When D and E do not happen to be the same size, E's drop behavior is incorrectly executed in the wrong location. The reference received by the Drop impl may point left or right of the real E value that is meant to be getting dropped.

In both cases, when the Report contains an error E that has nontrivial drop behavior, the most likely outcome is memory corruption.

When the Report contains an error E that has trivial drop behavior (for example a Utf8Error) but where D has nontrivial drop behavior (such as String), the most likely outcome is that downcasting to E would leak D.

Previous versions of tracing-subscriber were vulnerable to ANSI escape sequence injection attacks. Untrusted user input containing ANSI escape sequences could be injected into terminal output when logged, potentially allowing attackers to:

• Manipulate terminal title bars
• Clear screens or modify terminal display
• Potentially mislead users through terminal manipulation

In isolation, impact is minimal, however security issues have been found in terminal emulators that enabled an attacker to use ANSI escape sequences via logs to exploit vulnerabilities in the terminal emulator.

This was patched in PR #3368 to escape ANSI control characters from user input.

In the unique reclaim path of BytesMut::reserve, the condition

if v_capacity >= new_cap + offset

uses an unchecked addition. When new_cap + offset overflows usize in release builds, this condition may incorrectly pass, causing self.cap to be set to a value that exceeds the actual allocated capacity. Subsequent APIs such as spare_capacity_mut() then trust this corrupted cap value and may create out-of-bounds slices, leading to UB.

This behavior is observable in release builds (integer overflow wraps), whereas debug builds panic due to overflow checks.

PoC

use bytes::*;

fn main() {
    let mut a = BytesMut::from(&b"hello world"[..]);
    let mut b = a.split_off(5);

    // Ensure b becomes the unique owner of the backing storage
    drop(a);

    // Trigger overflow in new_cap + offset inside reserve
    b.reserve(usize::MAX - 6);

    // This call relies on the corrupted cap and may cause UB & HBO
    b.put_u8(b'h');
}

Workarounds

Users of BytesMut::reserve are only affected if integer overflow checks are configured to wrap. When integer overflow is configured to panic, this issue does not apply.

Impact

When user-provided input is provided to any type that parses with the RFC 2822 format, a denial of service attack via stack exhaustion is possible. The attack relies on formally deprecated and rarely-used features that are part of the RFC 2822 format used in a malicious manner. Ordinary, non-malicious input will never encounter this scenario.

Patches

A limit to the depth of recursion was added in v0.3.47. From this version, an error will be returned rather than exhausting the stack.

Workarounds

Limiting the length of user input is the simplest way to avoid stack exhaustion, as the amount of the stack consumed would be at most a factor of the length of the input.