CVE-2026-33894: Forge has signature forgery in RSA-PKCS due to ASN.1 extra field
(updated )
RSASSA PKCS#1 v1.5 signature verification accepts forged signatures for low public exponent keys (e=3). Attackers can forge signatures by stuffing “garbage” bytes within the ASN structure in order to construct a signature that passes verification, enabling Bleichenbacher style forgery. This issue is similar to CVE-2022-24771, but adds bytes in an addition field within the ASN structure, rather than outside of it.
Additionally, forge does not validate that signatures include a minimum of 8 bytes of padding as defined by the specification, providing attackers additional space to construct Bleichenbacher forgeries.
References
- datatracker.ietf.org/doc/html/rfc2313
- github.com/advisories/GHSA-ppp5-5v6c-4jwp
- github.com/digitalbazaar/forge
- github.com/digitalbazaar/forge/security/advisories/GHSA-cfm4-qjh2-4765
- github.com/digitalbazaar/forge/security/advisories/GHSA-ppp5-5v6c-4jwp
- mailarchive.ietf.org/arch/msg/openpgp/5rnE9ZRN1AokBVj3VqblGlP63QE
- nvd.nist.gov/vuln/detail/CVE-2026-33894
- www.rfc-editor.org/rfc/rfc8017.html
Code Behaviors & Features
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