CVE-2026-119196

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.

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-407

Published

2026-10-29

Modified

2026-10-29

Record from

the NVD, synced 2026-10-29

References

• https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c
• https://github.com/pyasn1/pyasn1/pull/132
• https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5
• https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5

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