Cyber Resilience

CVE-2026-21895

Rustcrypto Rsa ≤ 0.9.10

Published
08 January 2026
Modified
12 March 2026
Patch / advisory
View advisory
CVSS Score v4 2.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0041 34th percentile
Risk Priority 33 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-21895 is a low-severity Improper Check or Handling of Exceptional Conditions (CWE-703) vulnerability in Rustcrypto Rsa. Its CVSS base score is 2.7 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 34th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-24 (Fail in Known State) and SI-17 (Fail-safe Procedures) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

The `rsa` crate is an RSA implementation written in rust. Prior to version 0.9.10, when creating a RSA private key from its components, the construction panics instead of returning an error when one of the primes is `1`. Version 0.9.10…

more

fixes the issue.

CWE(s)
CWE-703

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-49092Same product: Rustcrypto Rsa
CVE-2026-50185Same vendor: Rustcrypto
CVE-2023-28959Shared CWE-703
CVE-2025-3084Shared CWE-703
CVE-2022-22265Shared CWE-703
CVE-2023-35867Shared CWE-703
CVE-2024-21593Shared CWE-703
CVE-2024-51491Shared CWE-703
CVE-2023-32230Shared CWE-703
CVE-2025-13021Shared CWE-703

Affected Assets

rustcrypto
rsa
≤ 0.9.10

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SC-24 Fail in Known State good match

Enforces failure to a known state while preserving required properties, limiting impact of unhandled exceptions.

SI-17 Fail-safe Procedures good match

Mandates explicit fail-safe procedures triggered by indicated failures, structurally preventing unhandled exceptional conditions.

SA-8 Security and Privacy Engineering Principles partial match

Requires application of security engineering principles that include robust exception and error handling during design.

SI-11 Error Handling partial match

Requires generation of safe, actionable error messages that directly addresses proper handling of exceptional conditions.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices explicitly require anticipating and correctly handling exceptional conditions during design and coding.

References