Cyber Resilience

CVE-2026-1229

Cloudflare Circl ≤ 1.6.3

Published
24 February 2026
Modified
03 March 2026
Patch / advisory
View advisory
CVSS Score v4 2.9
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L/E:P/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:N/AU:Y/R:X/V:X/RE:X/U:Amber
EPSS Score 0.0040 33th percentile
Risk Priority 25 floored blend · peak EPSS

Summary

CVE-2026-1229 is a low-severity Incorrect Calculation (CWE-682) vulnerability in Cloudflare Circl. Its CVSS base score is 2.9 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 33th 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 SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-1229 is a vulnerability in the CombinedMult function within the CIRCL ecc/p384 package, specifically for the secp384r1 elliptic curve. This function produces an incorrect value for certain inputs due to incomplete addition formulas. The issue affects the CIRCL library developed by Cloudflare, a Go-based cryptographic library. Notably, ECDH key exchange and ECDSA signing operations relying on this curve are not impacted.

The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating it can be exploited remotely by unauthenticated attackers with low complexity and no user interaction. Attackers could provide specific inputs to trigger the faulty computation in applications using the affected function, potentially leading to high impacts on confidentiality, integrity, and availability through cryptographic miscalculations.

The bug was addressed in CIRCL version 1.6.3, released with a fix implementing complete addition formulas. Additional details are available in the project's GitHub repository at https://github.com/cloudflare/circl and the specific release notes at https://github.com/cloudflare/circl/releases/tag/v1.6.3. Security practitioners should update to v1.6.3 or later to mitigate the issue.

EU & UK References

Vulnerability Data

The CombinedMult function in the CIRCL ecc/p384 package (secp384r1 curve) produces an incorrect value for specific inputs. The issue is fixed by using complete addition formulas. ECDH and ECDSA signing relying on this curve are not affected. The bug was…

more

fixed in v1.6.3 https://github.com/cloudflare/circl/releases/tag/v1.6.3 .

CWE(s)
CWE-682

Related Threats

MITRE ATT&CK Enterprise Techniques

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 →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-1732Same product: Cloudflare Circl
CVE-2023-3766Same vendor: Cloudflare
CVE-2023-2512Same vendor: Cloudflare
CVE-2023-3040Same vendor: Cloudflare
CVE-2023-3036Same vendor: Cloudflare
CVE-2026-0933Same vendor: Cloudflare
CVE-2023-4241Same vendor: Cloudflare
CVE-2026-44498Shared CWE-682
CVE-2026-20270Shared CWE-682
CVE-2023-36980Shared CWE-682

Affected Assets

cloudflare
circl
≤ 1.6.3

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V15.2.2

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation directly exercises calculations and can discover incorrect or unintended results used in security decisions.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development processes and standards can enforce coding rules and tool usage that reduce introduction of calculation errors.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles applied during design and implementation can require verified algorithms and safe arithmetic that structurally avoid incorrect calculation results.

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 directly prevent incorrect calculations via reviews, testing, and verification in security-critical code.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

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

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance can detect calculation flaws before deployment.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates verification steps that catch incorrect calculations before they reach production.

A.8.26 Application security requirements partial match
prevents

Application security requirements can explicitly call for numeric accuracy and bounds checking.

A.8.27 Secure system architecture and engineering principles partial match
degrades

Secure architecture principles include input validation and safe arithmetic design that reduce calculation errors.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit unsafe arithmetic and require defensive checks against incorrect results.

References