pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 0.6.5
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The pyasn1 Python library, a generic ASN.1 encoder and decoder, is affected. An attacker who supplies specially crafted BER or CER data made of many constructed BIT STRING fragments can cause the decoder to consume excessive CPU time, which can stall or slow the application during decoding.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. This issue is fixed in version 0.6.5.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- pyasn1 pyasn1
fixed in 0.6.5