CVE-2020-36315Public exploitNetwork attack vector

Signature forgery via permissive PKCS#1 padding checks

Published Apr 7, 2021 · Updated Aug 4, 2024

Improper RSA signature verification in RELIC before 2020-08-01 allows attackers to forge PKCS#1 v1.5 signatures with low-exponent keys. The pad_pkcs1 routine in src/cp/relic_cp_rsa.c overwrites prefix-check failures and accepts padding bytes that are merely nonzero instead of requiring the prescribed values. Exploitation requires an RSA public exponent such as 3; RELIC does not generate such low-exponent keys by default, but its API permits applications to supply them.

CVSS severity5.3
Medium
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper RSA signature verification in RELIC before 2020-08-01 allows attackers to forge PKCS#1 v1.5 signatures with low-exponent keys. The pad_pkcs1 routine in src/cp/relic_cp_rsa.c overwrites prefix-check failures and accepts padding bytes that are merely nonzero instead of requiring the prescribed values. Exploitation requires an RSA public exponent such as 3; RELIC does not generate such low-exponent keys by default, but its API permits applications to supply them.

The record

CVE
CVE-2020-36315
Published
Apr 7, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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