Impact
The affected functions set environment variables without synchronization. On Unix-like operating systems, this can crash in multithreaded programs. Programs may segfault due to dereferencing a dangling pointer if an environment variable is read in a different thread than the affected functions. This may occur without the user's knowledge, notably in the Rust standard library or third-party libraries.
The affected functions from time 0.2.7 through 0.2.22 are:
time::UtcOffset::local_offset_at 
time::UtcOffset::try_local_offset_at 
time::UtcOffset::current_local_offset 
time::UtcOffset::try_current_local_offset 
time::OffsetDateTime::now_local 
time::OffsetDateTime::try_now_local 
The affected functions in time 0.1 (all versions) are:
time::at_utc 
time::at 
time::now 
time::tzset 
Non-Unix targets (including Windows and wasm) are unaffected.
Patches
Pending a proper fix, the internal method that determines the local offset has been modified to always return None on the affected operating systems. This has the effect of returning an Err on the try_* methods and UTC on the non-try_* methods.
Users and library authors with time in their dependency tree should perform cargo update, which will pull in the updated, unaffected code.
Users of time 0.1 do not have a patch and should upgrade to an unaffected version: time 0.2.23 or greater or the 0.3 series.
Workarounds
A possible workaround for crates affected through the transitive dependency in chrono, is to avoid using the default oldtime feature dependency of the chrono crate by disabling its default-features and manually specifying the required features instead.
Examples:
Cargo.toml:
chrono = { version = "0.4", default-features = false, features = ["serde"] }
chrono = { version = "0.4.22", default-features = false, features = ["clock"] }
Commandline:
cargo add chrono --no-default-features -F clock
Sources: