Net::IDN::Punycode versions before 2.301 for Perl allow a heap buffer overflow via unchecked writes past the output buffer in encode_puny...

What happened

Net::IDN::Punycode versions before 2.301 for Perl allow a heap buffer overflow via unchecked writes past the output buffer in encode_punycode. The XS backend builds the encoded label in the string buffer of the scalar it returns, sized from the input length. The loop that emits the digits of each code point checks for room before every write, but the write of the last digit of each round and the write of the terminating NUL do not, so an input whose encoded form fills the buffer writes past its end. Only the XS backend is affected. Encoding an attacker-supplied string corrupts the heap.

Affected versions

Unknown product: before 2.301 (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.