Excessive time spent checking invalid RSA public keys (CVE-2023-6237)
Published Last modified Sources: Siemens ProductCERT, Ubuntu, BSI, Msrc Update Guide, EUVD, CVE.org
What is affected, what to do
Issue summary: Checking excessively long invalid RSA public keys may take a long time. Impact summary: Applications that use the function EVP_PKEY_public_check() to check RSA public keys may experience long delays.
Update OpenSSL to version 3.0.13, OpenSSL to version 3.1.5, OpenSSL to version 3.2.1.
- Affected
- OpenSSL
lt 3.0.0..3.0.13 - OpenSSL
lt 3.1.0..3.1.5 - OpenSSL
lt 3.2.0..3.2.1
- OpenSSL
- Fixed in
- OpenSSL
3.0.13 - OpenSSL
3.1.5 - OpenSSL
3.2.1
- OpenSSL
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Metrics
5.9
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
5.9
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: Siemens ProductCERT, Ubuntu, BSI, Msrc Update Guide, EUVD, CVE.org
2.3 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 83.2
Show all metrics
- Severity
- Medium
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 89.95 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 5.9 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 5.9
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 2.3 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 83.2
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-606
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Issue summary: Checking excessively long invalid RSA public keys may take a long time. Impact summary: Applications that use the function EVP_PKEY_public_check() to check RSA public keys may experience long delays. Where the key that is being checked has been obtained from an untrusted source this may lead to a Denial of Service. When function EVP_PKEY_public_check() is called on RSA public keys, a computation is done to confirm that the RSA modulus, n, is composite. For valid RSA keys, n is a product of two or more large primes and this computation completes quickly. However, if n is an overly large prime, then this computation would take a long time. An application that calls EVP_PKEY_public_check() and supplies an RSA key obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function EVP_PKEY_public_check() is not called from other OpenSSL functions however it is called from the OpenSSL pkey command line application. For that reason that application is also vulnerable if used with the '-pubin' and '-check' options on untrusted data. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are affected by this issue.
Source: siemens_advisory, Ubuntu Security Notices, BSI CSAF, BSI WID Portal, Microsoft Security Update Guide, ENISA EUVD, cvelistv5, NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| OpenSSL | OpenSSL |
|
|
| Broadcom | Fabric OS |
|
|
| Dell | PowerScale OneFS |
|
|
| Dell | PowerScale OneFS Node Firmware Package |
|
|
| HPE | HP-UX OpenSSL Software |
|
|
| IBM | AIX |
|
|
| IBM | MQ |
|
|
| IBM | VIOS |
|
|
| NetApp | AFF |
|
|
| NetApp | FAS |
|
|
| Open Source | OpenSSL |
|
|
| tribe29 | checkmk |
|
|
| Xerox | FreeFlow Print Server |
|
|
Vendors and products
Affected operating systems
| Linux | ubuntu | openssl | focal |
| Linux | ubuntu | openssl | jammy |
| Linux | ubuntu | openssl | mantic |
Weakness classes (CWE)
CWE-606Unchecked Input for Loop Condition
Base
The product does not properly check inputs that are used for loop conditions, potentially leading to a denial of service or other consequences because of excessive looping.
Entry at MITRE CWE-606
References & sources
- openssl.orgOpenSSL Advisoryeuvd, Vendor advisory
- github.com3.0.13 git commiteuvd, Patch
- github.com3.1.5 git commiteuvd, Patch
- github.com3.2.1 git commiteuvd, Patch
- openwall.comlists/oss-security/2024/03/11/1x_transferred
- security.netapp.comadvisory/ntap-20240531-0007x_transferred
- Siemens ProductCERTproductcert/html/ssa-265688.html
- Siemens ProductCERTproductcert/html/ssa-331112.html
- Siemens ProductCERTproductcert/html/ssa-915275.html
- Siemens ProductCERTproductcert/html/ssa-769027.html
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedopenssl.org
New references:Show 8 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84dReference added —https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2aReference added —https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294Reference added —https://www.openssl.org/news/secadv/20240115.txtReference removed https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84d—Reference removed https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2a—Reference removed https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294—Reference removed https://www.openssl.org/news/secadv/20240115.txt—Source identifier: openssl-security@openssl.org
Record modifiedCVE Program
New references:- http://www.openwall.com/lists/oss-security/2024/03/11/1
- https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84d
- https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2a
- https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294
and 2 more references
Show 12 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —http://www.openwall.com/lists/oss-security/2024/03/11/1Reference added —https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84dReference added —https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2aReference added —https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294Reference added —https://security.netapp.com/advisory/ntap-20240531-0007/Reference added —https://www.openssl.org/news/secadv/20240115.txtReference removed http://www.openwall.com/lists/oss-security/2024/03/11/1—Reference removed https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84d—Reference removed https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2a—Reference removed https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294—Reference removed https://security.netapp.com/advisory/ntap-20240531-0007/—Reference removed https://www.openssl.org/news/secadv/20240115.txt—Source identifier: af854a3a-2127-422b-91ae-364da2661108
Record modifiedSiemens ADP
Show 9 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2023/6xxx/CVE-2023-6237.json">CVE-2023-6237</a>Reference added —https://cert-portal.siemens.com/productcert/html/ssa-265688.htmlReference added —https://cert-portal.siemens.com/productcert/html/ssa-331112.htmlReference added —https://cert-portal.siemens.com/productcert/html/ssa-769027.htmlReference added —https://cert-portal.siemens.com/productcert/html/ssa-915275.htmlReference removed https://cert-portal.siemens.com/productcert/html/ssa-265688.html—Reference removed https://cert-portal.siemens.com/productcert/html/ssa-331112.html—Reference removed https://cert-portal.siemens.com/productcert/html/ssa-769027.html—Reference removed https://cert-portal.siemens.com/productcert/html/ssa-915275.html—Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
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<a href="https://intel.neosec.eu/en/cve/CVE-2023-6237"><img src="https://intel.neosec.eu/badge/cve/CVE-2023-6237.svg?lang=en" alt="CVE-2023-6237 – NEOSEC Intel" height="20"></a>